A jig assembly for a car body including a movable jig unit having a frame with a universal configuration and removable jig members configured exclusively for a distinctive body part; and a fixed station jig unit for positioning and fixing the movable unit. The fixed unit is comprised of an elevator lifter for supporting the frame, reference pins which are provided in the elevation range of the lifter and are inserted into the frame to position the frame in the longitudinal direction, reference blocks for positioning the lower end of the frame, first clamp units for fixing the frame onto the reference blocks, and second clamp units for securing a body part to the jig members.