A vehicle seat position adjusting device includes a slide adjuster having a slide lock mechanism, a reclining adjuster, and a walk-in mechanism disposed between the slide adjuster and the reclining adjuster. The walk-in mechanism includes a detecting plate for detecting rotation of the seat back relative to the seat cushion and the reclining adjuster includes a lower plate supported by the seat cushion, an upper plate supported by the seat back and rotatably supported on the lower plate, and a supporting surface formed in the upper plate or the lower plate which rotatably supports the detecting plate without increasing an axial width of the vehicle seat adjusting device.