A driver module structure includes a flexible circuit board (2) provided with a wiring pattern (7), a semiconductor device mounted on the flexible circuit board (2), and an electrically conductive heat-radiating member (4) joined to the semiconductor device. The wiring pattern (7) includes a ground wiring pattern (8). The flexible circuit board (2) has a cavity (9) that exposes a portion of the ground wiring pattern (8). The exposed portion of the ground wiring pattern (8) and the heat-radiating member (4) are connected to establish electrical continuity via a member (11) that is fitted into the cavity (9).