You can view a list of all the groups of which a user is a member. If the Google Groups for Business service is enabled (available in Google Apps for Business and Education), this list also includes any groups that the user owns.

To view a user's group memberships:

1. Sign in to the Google Admin console. 
2. Click Users. 
3. Find the user in the list.
   If necessary, first select the organization in which the user's account resides. Or, search for the user by typing his or her email address in the search field at the top of the Admin console and clicking Search accounts.
4. Click the link for the user.
5. On the user's profile page, under Groups, you'll see a list of the user's groups. For example: