To provide a seat slide device of a simple configuration by providing a locking mechanism to prohibit the rotation of either link out of a front link and a rear link.

In the seat slide device to move a seat cushion 53 in the longitudinal direction, a front link 61 in which an upper portion thereof is rotatably mounted on the seat cushion 53 and a lower portion thereof is rotatably mounted on a floor is provided on a front part of the seat cushion 53, and either a rear link 67 in which an upper portion thereof is rotatably mounted on the seat cushion 53 and a lower portion thereof is rotatably mounted on the floor or a slide mechanism capable of moving the seat cushion 53 along the seat cushion 53 is provided on a rear part of the seat cushion 53. A locking mechanism 71 to prohibit the rotation of the front link 61 is provided on the upper portion of the front link 61.