A vehicle body (B) is lowered toward a frame (F) from above, and fixed to the frame (F) via a mount insulator (MI). Prior to fixing, a locating jig (1) is attached to the frame (F). A locating hole (E) is formed in the body (B). While lowering the body (B), the horizontal position of the body (B) is adjusted such that the locating jig (1) penetrates the locating hole (E). The body (B) is aligned accurately with the frame (F) when a predetermined state of engagement is reached between the locating jig (1) and locating hole (E). In this state, a fastening bolt (G) which is passed through the mount insulator (MI) is used to fix the body (B) to the frame (F), and thus the fastening bolt (G) can be tightened without applying an eccentric load on the mount insulator (MI).