SEAT SLIDE DEVICE FOR VEHICLE

Provided is a seat slide device for a vehicle capable of enhancing the degree of design freedom in an interior height of a vehicle cabin, light-weighting the vehicle, and enhancing comfort in use when a seat is moved forward and rearward. The seat slide device for a vehicle includes: an upper rail (2) made of an aluminum alloy, including a sliding section (21) having a plurality of ball rolling grooves (23) each formed along a longitudinal direction of the upper rail (2) ; a lower rail (3) made of an aluminum alloy, including: a guide groove (31) for receiving the sliding section (21) of the upper rail (2) ; and ball rolling grooves (33) each formed in the guide groove (31) along a longitudinal direction of the lower rail (3) to be opposed to the plurality of ball rolling grooves (23) of the sliding section (21) ; and a large number of guide balls (4) each made of a synthetic resin, for supporting movement of the upper rail (2) relative to the lower rail (3), the large number of guide balls (4) being arrayed in line without using a cage in a portion between each of the plurality of ball rolling grooves (23) and each of the ball rolling grooves (33).