Disclosed herein is a locking guide of a locking device for a vehicle seat. The locking device comprises a lower rail, an upper rail coupled to the lower rail, a locking guide fixed to a bottom surface of the upper rail, a pair of lock members having a plurality of locking protrusions, a plurality of locking grooves engaged with the locking protrusions, and a lock spring. The locking guide is formed by pressing a plate member having a predetermined thickness. The locking guide comprises a bottom surface recessed in the locking guide, a guide body having a circumferential portion formed along edges of the bottom surface, guide holes formed through the bottom surface of the guide body such that the locking protrusions can enter or exit through the guide holes, supporting posts extended at the front and rear sides of the guide body to a height such that the supporting posts can be connected to the upper rail, and fixing flanges, each of which has a fixing hole and is bent at an end of the supporting post so as to be fixed to the upper rail.