An electronic circuit device including a circuit board having electronic parts, and a flexible wiring board for connection between the circuit board and external equipment. The circuit board has circuit-side connection terminals juxtaposed on a mount surface having the electrical parts mounted thereon or a non-mount surface. The wiring board has terminals juxtaposed on one of the surfaces thereof so that the wiring-board-side connection terminals confront the circuit-side circuit board connection terminals, and free-end portions each formed so as to include at least one of the wiring-board-side connection terminals, and the wiring board free-end portions are not adhesively attached to the circuit board, and the circuit-side connection terminals are electrically connected to the corresponding wiring-board-side connection terminals while the circuit-side connection terminals confront the wiring-board-side connection terminals.