A head driving mechanism includes a first cam follower an end portion of which is attached to a first holding unit and the other end portion of which includes a first sliding-contact surface disposed in sliding contact with a cam, and a second cam follower an end portion of which is attached to the second holding unit and the other end portion of which includes a second sliding-contact surface disposed in sliding contact with the cam. The first cam follower and the second cam follower are each displaced by rotation of the cam so as to move the first printing head and the second printing head, while the first sliding-contact surface and the second sliding-contact surface are in sliding contact with an outer circumferential surface of the cam.