An information processing apparatus is disclosed which handles content items categorized in a predetermined number of groups. The apparatus includes group number attaching means for attaching to the groups a series of group numbers made up of natural numbers starting from 1; and depth information attaching means for attaching depth information 1 to the group having the group number 1. If a given group with a group number N which is a natural number has depth information “a” which is also a natural number, then the depth information attaching means attaches the depth information formed by a natural number which is at least 1 and not more than a+1 to the group having the group number N+1.