A vehicle window opening/closing device 1 comprises: an inversion pulley 12 provided to an upper portion of a guide rail 10; a drive mechanism 14 provided, in line, to a lower end of the guide rail 10, and constituted so that a speed reduction mechanism including a worm and a worm wheel, and a drum connected concentrically with the worm wheel are received into a same housing 15; a close-side cable 24, whose one end is fixed to the drum and whose other end is coupled to a carrier plate 11 via the inversion pulley 12; an open-side cable 25, whose one end is fixed to the drum and whose other end is coupled directly to the carrier plate 11; and an electric motor 17 having an armature coupled mechanically to the worm, the electric motor being capable of being coupled to the drive mechanism 14.