1. An item recommendation system comprising: a feedback receiving unit receiving feedback for one of a plurality of items from one of a plurality of users, wherein the feedback includes information for at least one action of a purchase, evaluation, or detail access; a feedback history storage unit storing the received feedback and past received feedback from the plurality of users, wherein the received feedback and past feedback are stored as combinations of users and items having feedback given by the users; a relevance calculation unit calculating, when feedback is received by the feedback receiving unit, a degree of relevance between the one of the plurality of items and another one of the plurality of items, based on first information indicating a degree and temporal sequence of feedback given by the one of the plurality of users for at least one of the plurality of items, and second information indicating a degree of past feedback given by the plurality of users to the plurality of items stored in the feedback history storage unit; and a recommendation unit recommending, upon receiving feedback by the feedback receiving unit, one or more of the plurality of items to the one of the plurality of users, the recommended items having high relevance to the one of the plurality of items, wherein the recommended items are selected based on the degree of relevance calculated by the relevance calculation unit.