A printed wiring board (10) has mounted thereon a power module (20) that has both a plurality of lead terminals (21) for soldering and at least one screw terminal (22) for screw tightening and is provided with through holes (1) into which the lead terminals (21) are introduced and are soldered, and an electrode part (3) on which a screw introduction hole (4) with which the screw terminal (22) is tightened via a screw (23) is formed. A channel part (6) that cuts across two common tangent lines (11a, 11b) that join the periphery of a contact region (5) for the electrode part (3) that a head seat surface (23c) of the screw (23) or a washer (23d) contacts and the periphery of a land part (2) of the through holes (1) is provided between the electrode part (3) and the through holes (1).