Appropriately sharing user information. An information sharing system includes: a specific information acquisition unit that acquires specific information of each terminal from a plurality of user terminals which are carried by users; a user information acquisition unit that acquires user information from the plurality of user terminals; an information management unit that encrypts the user information that is acquired by the user information acquisition unit on the basis of the specific information that is acquired by the specific information acquisition unit; a state acquisition unit that acquires the specific information of a user terminal that accesses a network including a sharing device from the sharing device that is a terminal other than the user terminals; and a sharing unit that shares the user information by decoding the user information that is encrypted by the information management unit with the specific information that is acquired by the state acquisition unit.