A seat sliding structure for a vehicle, comprising: a pair of left and right slide rails that include upper rails, which are configured to be attached to a lower portion of a vehicle seat, and lower rails, which support the upper rails such that the upper rails can slide in a vehicle longitudinal direction; rail guiding members that are configured to be fixed to a floor panel, and that support the lower rails such that the lower rails can slide in the vehicle longitudinal direction between a driving position at a vehicle front side and a relaxation position at a vehicle rear side; characterized in that the seat sliding structure for a vehicle comprises a locking mechanism that is configured to lock movement of the slide rails at the relaxation position, and to release a locked state when a frontal collision of the vehicle is detected or predicted; a damping mechanism that, at a time of frontal collision of the vehicle, damps inertial movement of the slide rails from the relaxation position toward the vehicle front side; the damping mechanism includes rods (61, 68) that are provided below the slide rails and that extend in the vehicle longitudinal direction, of which at least rear portions are configured to move upward, pop-up devices (69, 70, 71) that, when operated, move the rods (61, 68) upward, and rod receiving portions that move together with the slide rails; the pop-up devices (69, 70, 71) are configured to be operated when the slide rails are at the relaxation position and a frontal collision of the vehicle is detected or predicted; and the rod receiving portions engage with the rear portions of the rods that have moved upward, and, in conjunction with inertial movement of the slide rails toward the vehicle front side, crush the rods in axial directions. a pair of left and right slide rails that include upper rails, which are configured to be attached to a lower portion of a vehicle seat, and lower rails, which support the upper rails such that the upper rails can slide in a vehicle longitudinal direction; rail guiding members that are configured to be fixed to a floor panel, and that support the lower rails such that the lower rails can slide in the vehicle longitudinal direction between a driving position at a vehicle front side and a relaxation position at a vehicle rear side; characterized in that the seat sliding structure for a vehicle comprises a locking mechanism that is configured to lock movement of the slide rails at the relaxation position, and to release a locked state when a frontal collision of the vehicle is detected or predicted; a damping mechanism that, at a time of frontal collision of the vehicle, damps inertial movement of the slide rails from the relaxation position toward the vehicle front side; the damping mechanism includes rods (61, 68) that are provided below the slide rails and that extend in the vehicle longitudinal direction, of which at least rear portions are configured to move upward, pop-up devices (69, 70, 71) that, when operated, move the rods (61, 68) upward, and rod receiving portions that move together with the slide rails; the pop-up devices (69, 70, 71) are configured to be operated when the slide rails are at the relaxation position and a frontal collision of the vehicle is detected or predicted; and the rod receiving portions engage with the rear portions of the rods that have moved upward, and, in conjunction with inertial movement of the slide rails toward the vehicle front side, crush the rods in axial directions.