To provide a collar/frame coupling body which comprises a metal frame of a hollow closed-sectional structure having a pair of flat wall parts facing each other and a collar which is disposed at a position corresponding to a bolt hole formed in each of the flat wall parts across a frame hollow part, is tightened to a supporting member by bolts passing through the collar and the bolt holes, and capable of firmly and efficiently fixing the collar to the metal frame at low cost without using any welding means.

A collar C is held between surfaces facing each other of a pair of flat wall parts Wu and Wd of a frame 1 at the fitting position Xc. The frame 1 is formed so as to advance the collar C to the fitting position Xc from an opening end O thereof. An engagement claw part 3 which is engaged with the opening edge of the collar C to fix the collar C to the frame 1 is integrated with the opening edge part of a bolt hole h of one flat wall part Wu by burring.