An operation mechanism attaches a movable member to a main body to be rotatable between a first position and a second position. The movable member is held in the first position by a locking device. The operation mechanism includes a base attached to the main body, a contact portion attached to the movable member, and a coil spring having one end fixed to the base, and the other end attached to the contact portion for urging the movable member in the first position toward the second position. A transfer track for the contact portion is formed at the base. By the transfer track, after the movable member in the first position is moved to a predetermined position by a force accumulated on the spring, when the movable member is pushed to the second position, the spring stores a force from the predetermined position to the second position.