Use bellow code

<apex:variable var="index" value="{!1}"/>
<apex:repeat value="{!yourList}" var="ob">
    <apex:outputLabel value="{!index}"/>
    <apex:variable var="index" value="{!index+1}"/>
</apex:repeat>

You can use an apex:variable, as shown in the code below, to show a row number.

<apex:variable var="index" value="{!1}"/>
<apex:repeat value="{!yourList}" var="ob">
    <apex:outputLabel value="{!index}"/>
    <apex:variable var="index" value="{!index+1}"/>
</apex:repeat>