To prevent a fastening force of a bolt for connecting a cabin and a side member from being weakened even after a long period of time as less as possible.

In this cabin coupling structure of an automobile, a cabin 4 is mounted on a side member 1 via an insulator 2, and a collar 5 reaching the cabin 4 from the side member 1 is provided. The bolt 6 penetrates through the cabin 4, the collar 5, and the side member 1, and a nut 9 is fastened with the bolt 6, so that the side member 1 is coupled with the cabin 4. A spherical seat 12 is formed on the cabin 4, and a semi-spherical washer 8 is slide-contactably and rotatably stored in the spherical seat 12. The bolt 6 is inserted in the washer 8 and the spherical seat 12, and a head 6A of the bolt 6 is supported by the washer 8. A screw part 6B of the bolt 6 is inserted in the side member 1, the insulator 3, and a supporting plate 16, and the nut 9 is fastened with the screw part 6B, so that the cabin 4 is fixed to the side member 1.