A window opening/closing device (1) for a vehicle has an inversion pulley (12) provided at the upper portion of a guide rail (10); a drive mechanism (14) provided continuously to the lower end of the guide rail (10) and having a reduction mechanism and a drum that are received in the same housing (15), the reduction mechanism consisting of a worm and a worm wheel, the drum being coaxially joined with the worm wheel; a closing-side cable (24) having one end secured to the drum and the other end connected to a carrier plate (11) via the inversion pulley (12); an opening-side cable (25) having one end secured to the drum and the other end directly connected to the carrier plate (11); and an electric motor (17) having an armature that is mechanically connected to the worm and capable of beingconnected to the drive mechanism (14).