A power transmission apparatus and a rotation apparatus are disclosed. A power transmission apparatus that includes: a power generating part, which includes a drive axis; a worm, which is joined to the drive axis; a worm gear, which meshes with the worm, and which includes an output axis configured to transmit power; and a friction hinge, which is joined to the output axis, and which is configured to engage and disengage a rotational force of the output axis, can provide sufficiently high deceleration and high torque, even when a low-capacity motor having a low cogging torque is used. Also, the power transmission apparatus can be made safer and less noisy for not only automatic operation by the motor but also manual operation by a user, while the gear module, motor, etch, can be protected from excessive loads.