A power seat slide apparatus includes: a housing fixedly mounted on the first rail and possessing a reverse U-shaped cross section projecting upwardly with an upper wall, which forms an upper surface of the reverse U-shaped cross section, and first and second sidewalls, which forms side surfaces of the reverse U-shaped cross section. The housing further includes a notch defined by a first notch end surface of the upper wall and a second notch end surface of the first and second sidewalls. A nut member is fitted into the notch of the housing, supported inside the housing, and is held tight in the longitudinal direction of the vehicle by the first notch end surface and the second notch end surface. A screw shaft is freely rotatably supported by the second rail and is engaged with the nut member.