The present invention provides a fixing device 1 for a position-adjusting jig, the fixing device 1 including: a driving cylinder 100 which includes a piston having a predetermined stroke; a jig-position-fixing unit 200 which is coupled to the piston of the driving cylinder 100; a guide block 300 which fixes and assists the jig-position-fixing unit 200 operated by the stroke of the piston of the driving cylinder 100; and a position-fixing bracket 400 which is coupled to a position-adjustable jig B so that the position-adjustable jig B is fixed by the jig-position-fixing unit 200. Therefore, the present invention is applied to various working processes in which a jig A is used, such that it is possible to reduce time required to fix the jig A to the existing predetermined position to produce products with higher quality and perform an operation, and as a result, it is possible to prevent a loss of labor productivity, thereby ensuring and improving productivity of the products.