If you need info of the Opportunity record of the approval, I think the standard report will not work.
There is an idea for that: https://success.salesforce.com/ideaView?id=08730000000l7SVAAY
From this blog: http://cherfeldman.blogspot.com/2014/01/potential-solution-for-reporting-on.html
Potential Solution:
Add a custom object called “Approval History Reporting” to be a child object of opportunities through a master detail relationship.
Add the following fields to the custom object:
Approval History Start Date/Time
Approval History End Date/Time
Approver – lookup to user
- Approver Changed to – lookup to user From
Approval Status (picklist) – Submitted, Approved, Rejected, Recalled
To Approval Status (picklist) – Submitted, Approved, Rejected,
Recalled Approver Comments text field
Age = formula field to calculate Approval History End – Approval
History Start, show number in hours
How this object will work
Records will be inserted and/or updated when certain things happen.
Scenario 1: Opportunity is submitted for approval
Upon initial submission of an opportunity to an approval process a record will be inserted into the Approval History Reporting with the following fields populated:
Approval History Start Date/Time – Time opportunity was submitted for approval
Approver – user selected as approver
From Approval Status = Blank
To Approval Status = Submitted
Scenario 2: Opportunity is Approved by Approver:
Existing record with To Status of Submitted will update to have an Approval End Date/Time of the time the stage changed
New record will insert with the following information:
Approval History Start Date/Time – Time opportunity was approved
Approver – user selected as approver
From Approval Status =Submitted
To Approval Status = Approved
Comments = any comments entered by approver
Scenario 3: Opportunity is Rejected by Approver:
Existing record with To Status of Submitted will update to have an Approval End Date/Time of the time the stage changed
New record will insert with the following information:
Approval History Start Date/Time – Time opportunity was Rejected
Approver – user selected as approver
From Approval Status =Submitted
To Approval Status = Rejected
Comments = any comments entered by approver
Scenario 4: Opportunity is Recalled by User:
Existing record with To Status of Submitted will update to have an Approval End Date/Time of the time the stage changed
New record will insert with the following information:
Approval History Start Date/Time – Time opportunity was Recalled
Approver – user selected as approver
From Approval Status =Submitted
To Approval Status = Recalled
Comments = any comments entered by approver
Scenario 5: Approver is reassigned
Existing record that is submitted with no End time will have the Approver Changed To lookup update to the new approver
Scenario 6: Opportunity is Recalled and User Submits Again
New record will be inserted with the following information
Approval History Start Date/Time – Time opportunity was submitted for approval
Approver – user selected as approver
From Approval Status = Recalled
To Approval Status = Submitted
Scenario 7: Opportunity is Rejected and User Submits Again
New record will be inserted with the following information
Approval History Start Date/Time – Time opportunity was submitted for approval
Approver – user selected as approver
From Approval Status = Rejected
To Approval Status = Submitted
Scenario 8: Opportunity is Approved and user hits validation due to product/pricing changes and is forced to submit again
New record will be inserted with the following information
Approval History Start Date/Time – Time opportunity was submitted for approval
Approver – user selected as approver
From Approval Status = Approved
To Approval Status = Submitted