Abstract: The rotation operation plane of the ring-shaped operation members that operate the rotation is inclined with respect to the horizontal plane so that the rotation operation of the ring-shaped operation member can be performed without holding a finger in the vertical direction. Furthermore, since the rotation operation plane is inclined with respect to the placement plane of the case, static friction on the placement plane is generated by a force component of the operation force acting on the rotation operation plane and is perpendicular to the placement plane, thus the case does not move toward the rotation operation direction during the rotation operation.