To improve the holding force of a clip on a seat portion while uniformly reducing the thickness of the seat portion to avoid shrinkage cavities in the surface (the designed face) of a plate member when molded.

In this two-member assembling structure, the resin clip 10 for assembling the resin plate member 30 and another member together is fastened to the cylindrical seat portion 32 integrally molded on a reverse face 30b of the plate member 30. A body 12 of the clip is hollow-shaped to be applied and mounted onto the seat portion 32 of the plate member 30. The body 12 has a supporting shaft 14 to be inserted into the seat portion 32, and a fastening blade 16 to be bitten into a fastened face 32a of the seat portion 32 by axially rotating the clip 10 relative to the seat portion. Inside the seat portion 32, a rib 34 is provided which is protruded from the inside of the fastened face 32a to contact the supporting shaft 14.