An electric circuit board system for a camera includes at least one main electric circuit board having a central processing unit for performing a control of a camera, and at least one connection section for having an electric connection with other electric circuit boards. A plurality of unit circuit boards can be connected with the above-described at least one connection section, with mutually different specifications. Any one optional unit circuit board is selected from the plurality of unit circuit boards and is connected to at least one of the main electric circuit boards, for structuring a camera.