A vehicle seat supported such that an upper rail connected to a seat body is capable of sliding in a seat front-rear direction relative to a lower rail fixed at the vehicle body side through a pair of slide guides (42, 44) disposed in a row along the seat front-rear direction, wherein: the separation between the seat front-rear direction central portion of a first of the slide guides (42, 44) and the seat front-rear direction central portion of the second of the slide guides (42, 44) is narrower than half the maximum slide amount of the upper rail with respect to the lower rail; the upper rail comprises a front upper projection portion and a rear upper projection portion disposed further to the seat rear side than the front upper projection portion; the lower rail comprises a front lower projection portion and a rear lower projection portion disposed further to the seat rear side than the front lower projection portion; the upper rail is restricted from sliding towards the seat front side with respect to the lower rail by the first slide guide, which is disposed at the center between the rear upper projection portion and the front lower projection portion in a state in which the upper rail is disposed at the center of its sliding range with respect to the lower rail, being sandwiched between the rear upper projection portion and the front lower projection portion; and the upper rail is restricted from sliding towards the seat rear side with respect to the lower rail by the second slide guide, which is disposed at the center between the front upper projection portion and the rear lower projection portion in a state in which the upper rail is disposed at the center of the sliding range with respect to the lower rail, being sandwiched between the front upper projection portion and the rear lower projection portion; characterized in that: the lower rail comprises a projection portion projecting out towards the opposing rail side in the vehicle up-down direction at the front end portion or the rear end portion or both the front and rear end portions and suppressing bowing of the upper rail towards the lower rail by making contact with the opposing rail in the vehicle up-down direction, wherein the projection portion is employed in common with the front lower projection portion or the rear lower projection portion. the separation between the seat front-rear direction central portion of a first of the slide guides (42, 44) and the seat front-rear direction central portion of the second of the slide guides (42, 44) is narrower than half the maximum slide amount of the upper rail with respect to the lower rail; the upper rail comprises a front upper projection portion and a rear upper projection portion disposed further to the seat rear side than the front upper projection portion; the lower rail comprises a front lower projection portion and a rear lower projection portion disposed further to the seat rear side than the front lower projection portion; the upper rail is restricted from sliding towards the seat front side with respect to the lower rail by the first slide guide, which is disposed at the center between the rear upper projection portion and the front lower projection portion in a state in which the upper rail is disposed at the center of its sliding range with respect to the lower rail, being sandwiched between the rear upper projection portion and the front lower projection portion; and the upper rail is restricted from sliding towards the seat rear side with respect to the lower rail by the second slide guide, which is disposed at the center between the front upper projection portion and the rear lower projection portion in a state in which the upper rail is disposed at the center of the sliding range with respect to the lower rail, being sandwiched between the front upper projection portion and the rear lower projection portion; characterized in that: the lower rail comprises a projection portion projecting out towards the opposing rail side in the vehicle up-down direction at the front end portion or the rear end portion or both the front and rear end portions and suppressing bowing of the upper rail towards the lower rail by making contact with the opposing rail in the vehicle up-down direction, the lower rail comprises a projection portion projecting out towards the opposing rail side in the vehicle up-down direction at the front end portion or the rear end portion or both the front and rear end portions and suppressing bowing of the upper rail towards the lower rail by making contact with the opposing rail in the vehicle up-down direction,