A vehicular seat slide device, includes: a first rail fixed to one of a vehicular floor and a seat; a second rail fixed to the other one of the floor and the seat, and linked to be movable relative to the first rail; a screw rod supported by the second rail to be rotatable around an axial line which extends in a moving direction; a metal case fixed to the first rail, and through which the screw rod is inserted; a resin nut housed in the metal case in a state of being unmovable in the moving direction with respect to the metal case, and screwed to the screw rod; and a metal nut housed in the metal case in a state of not being in contact with the resin nut in the moving direction, and screwed to the screw rod.