In printed boards arranged in a vertical relationship, outer peripheral portions of an upper printed board are projected outward from outer peripheral portions of a lower printed board. Conductive bodies with terminal holes are arranged side by side on the upper and the lower printed boards along peripheral edges of the boards. Press-fit terminals are arranged in row arrangement along the outer peripheral portions of the printed boards. Each of the press-fit terminals is pressed from below into terminal holes of the two upper and lower printed boards with a long first vertical portion outside and a short second vertical portion inside. This results that a press-fit portion of the second vertical portion is pressed and brought into contact with a terminal hole in a conductive body on a peripheral edge of the lower printed board, a press-fit portion of the first vertical portion is pressed and brought into contact with a terminal hole in a conductive body on a peripheral edge of the upper printed board, and a horizontal portion is supported from below by a step-like portion projected from a printed board retaining case.