The electronic device can be used with an accessory module that is a second device attached to a device main body that is a first device. The accessory module includes a locking member that is held so as to be able to be turned. The locking member includes a ring-shaped portion that has a plurality of claw portions and an operation portion for performing a turning operation. The device main body 1 includes a plurality of claw portions corresponding to the plurality of claw portions of the locking member. The claw portions and the claw portions engage with each other in a state in which the accessory module is attached to the device main body by the turning operation of the operation portion, and the claw portions and the claw portions are not engaged in a state in which the accessory module can be removed from the device main body.