PURPOSE: To obtain a stable and exact electric power source, by providing an electric power source adaptor having a large capacity battery so as to be freely detachable, in a camera using electric power for various controls.

CONSTITUTION: A right side circuit 1 of a 1 point chain line shows a built-in part of a camera, and a left side circuit 11 shows an electric power source adaptor which is freely detachable. In a state that the adaptor is not installed, switches SW2a and SW2b are switched to sides a1 and b1, respectively, and a low voltage driving circuit 21 and a high voltage driving circuit 22 are driven by a battery E1a, and batteries E1a and E1b, respectively. When the electric power source adaptor 11 connected with a camera by 4 terminals t1Wt4 is installed, the switches SW2a and SW2b are switched to sides a2 and b2, respectively, and the low voltage circuit 21 is driven by an electric power source having a comparatively large capacity such as an alkali dry battery, and also the high voltage circuit 22 is driven through a boosting circuit 31.