A setting/operating device includes a first motor; a sun gear that rotates by receiving a rotating force from the first motor; a first internal gear disposed so as to surround the sun gear; a second motor that applies a force to the first internal gear in a direction in which rotation of the first internal gear is prevented; a plurality of planetary gears disposed between the sun gear and the first internal gear, engaged with the sun gear and the first internal gear, and capable of rotating on the axes thereof while revolving around the sun gear; a rotation mechanism that rotates by receiving rotating forces of the plurality of planetary gears; an output shaft that is coupled to the rotation mechanism; and a spring unit that applies a rotating force to the output shaft when supply of electric power to the first motor and the second motor is stopped.