To make user-friendliness excellent and to cope with faulty communication.

A stroboscopic device 30 detachably attached to an imaging apparatus 1 includes: a non-contact information transmission means 213 transmitting a first piece of information in a non-contact state according as the stroboscopic device 30 is attached to the imaging apparatus; and a communication means 200 performing communication with the imaging apparatus through a contact group 39. The non-contact information transmission means is constituted not to transmit the first information when a main switch 211 of the stroboscopic device is OFF, and notifies the imaging apparatus of attachment of the stroboscopic device and ON of the main switch by causing the imaging apparatus to receive the first information. The communication means transmits a second piece of information for determining whether communication with the imaging apparatus is satisfactorily performed.