A vehicle seat sliding apparatus comprising: a first rail adapted to be fixed to.any one of a vehicle floor and a seat; and a second rail adapted to be fixed to the other one of the vehicle floor and the seat and adapted to be connected to the first rail so as to be capable of relative movement with respect to the first rail, the first rail including: a pair of side wall portions juxtaposed on both sides in terms of the widthwise direction; a connecting wall portion connecting proximal ends of the both side wall portions; and first folded-back wall portions protruded from distal ends of the both side wall portions in the widthwise direction and then folded back toward proximal end sides of the side wall portions, the second rail including: a pair of second folded-back wall portions protruded from both sides in the widthwise direction and then folded back so as to be surrounded by the side wall portions and the first folded-back wall portions; an in-rail functional portion formed at an end portion of the first rail in terms of the longitudinal direction so as to project into an internal space(s) formed by the first rail to achieve a predetermined function; being characterised by further comprising a recessed portion formed around the in-rail functional portion in association with the formation of the in-rail functional portion; and a protector adapted to be mounted on an end portion of the first rail in terms of the longitudinal direction and cover the end portion thereof, wherein the protector is formed with a projection adapted to fit the recessed portion to couple the protector and the first rail. a first rail adapted to be fixed to.any one of a vehicle floor and a seat; and a second rail adapted to be fixed to the other one of the vehicle floor and the seat and adapted to be connected to the first rail so as to be capable of relative movement with respect to the first rail, the first rail including: a pair of side wall portions juxtaposed on both sides in terms of the widthwise direction; a connecting wall portion connecting proximal ends of the both side wall portions; and first folded-back wall portions protruded from distal ends of the both side wall portions in the widthwise direction and then folded back toward proximal end sides of the side wall portions, a pair of side wall portions juxtaposed on both sides in terms of the widthwise direction; a connecting wall portion connecting proximal ends of the both side wall portions; and first folded-back wall portions protruded from distal ends of the both side wall portions in the widthwise direction and then folded back toward proximal end sides of the side wall portions, the second rail including: a pair of second folded-back wall portions protruded from both sides in the widthwise direction and then folded back so as to be surrounded by the side wall portions and the first folded-back wall portions; an in-rail functional portion formed at an end portion of the first rail in terms of the longitudinal direction so as to project into an internal space(s) formed by the first rail to achieve a predetermined function; being characterised by further comprising a recessed portion formed around the in-rail functional portion in association with the formation of the in-rail functional portion; and a protector adapted to be mounted on an end portion of the first rail in terms of the longitudinal direction and cover the end portion thereof, wherein the protector is formed with a projection adapted to fit the recessed portion to couple the protector and the first rail. a pair of second folded-back wall portions protruded from both sides in the widthwise direction and then folded back so as to be surrounded by the side wall portions and the first folded-back wall portions; an in-rail functional portion formed at an end portion of the first rail in terms of the longitudinal direction so as to project into an internal space(s) formed by the first rail to achieve a predetermined function; being characterised by further comprising a recessed portion formed around the in-rail functional portion in association with the formation of the in-rail functional portion; and a protector adapted to be mounted on an end portion of the first rail in terms of the longitudinal direction and cover the end portion thereof, wherein the protector is formed with a projection adapted to fit the recessed portion to couple the protector and the first rail.