PURPOSE: To provide a butt joining structure of resin molded products used in the production of a resin cabinet by especially combining relatively large resin products, easy in alignment at the time of joining, reduced in the use quantity of joining members such as bolts or nuts and excellent in assembling easiness.

CONSTITUTION: Joining projections 12, 14, 16 are formed to the joining edge end parts 10, 11 of one resin cabinet constituting member 8 so as to protrude along the edge end parts 10, 11 and the fitting holes in which the joining projections 12, 14, 16 are fitted are formed to the joining edge end parts 18, 20 of the other resin cabinet constituting member 4 along the edge end parts in a width narrower than the thickness of the joining edge end parts 18, 20 along the edge end parts and resin cabinet constituting members 4, 6, 8 are constituted of a crosslinked polynorbornene resin.