Seat slide device for vehicles

A seat slide device for a vehicle is provided which comprises a lower rail, an upper rail and a lock mechanism for releasably locking the upper rail to the lower rail. The lock mechanism includes one or more locking fingers pivotally installed on an upper rail side, a plurality of engaged portions provided to a lower rail side, and a biasing unit for urging the one or more locking fingers in the direction to engage a corresponding number of the engaged portions. The one or more locking fingers and the biasing unit are disposed within a space between the upper rail and the lower rail. The lock mechanism further includes a lock plate having the engagement portions. The lock plate is an independent part, disposed within the space and secured to the lower rail.