In a cap fastening apparatus 10 in which a rotation of a motor 20 is transmitted to a chuck 50 while being decelerated by a speed reducer 40, and a cap 1 gripped by the chuck 50 is threadably attached to a bottle 2, a torque limiter apparatus 30 is interposed between the motor 20 and the speed reducer 40, the torque limiter apparatus 30 disconnecting a transmission of a rotation from the motor 20 to the chuck 50 at a time when a rotational resistance of the chuck 50 becomes larger than a set torque.