In synchronous interval photographing by a plurality of imaging apparatuses, an imaging apparatus functioning as a master clocks a photographing interval in the interval photographing, sequentially generates photographing instruction signals at clocked photographing intervals, instructs its own imaging section to perform image photographing every time a photographing instruction signal is generated, and transmits the photographing instruction signal to the other imaging apparatus. The imaging apparatus functioning as the slave instructs its own imaging section to perform image photographing every time a photographing instruction signal is received from the imaging apparatus functioning as the master.