1. A recommendation information generation apparatus comprising: a vector acquisition unit that acquires a user characteristic vector of each of users and includes: a receiving unit that receives a selection of one optional item from a plurality of optional items by a user operation; a storage unit that stores a satisfactory feature vector of the optional item that is received by the receiving unit and dissatisfactory feature vectors of optional items that are not received by the receiving unit; and a user characteristic vector generation unit that generates an orthogonal vector perpendicular to a separation plane that separates the satisfactory feature vector of the selected optional item and the dissatisfactory feature vectors of non-selected optional items, which are stored in the storage unit, as the user characteristic vector; a similarity calculation unit that calculates a degree of similarity between the users based on the user characteristic vector of each of the users that is acquired by the vector acquisition unit; a selection unit that selects a similar user who is similar to a first user based on the degree of similarity calculated by the similarity calculation unit; and a generation unit that includes a processor that generates recommendation information for the first user based on the characteristic vector of the similar user selected by the selection unit.