PURPOSE: To fully display the merit in the forming of a door, by preparing the door with a synthetic resin.

CONSTITUTION: A door 1 made of synthetic resin is used to form a main body 10 by adhesively jointing a door outer panel 11 to a door inner panel 12, and successively to an upper sash 22 of a door sash 2 a lower sash part 20 is integrally formed with the door inner panel 12. Then mounting portions 122 of door hinges 7, 8 at a front end wall 120 of the door inner panel 12 are formed in larger thickness than general portions, and to the mounting part of a hinge bolt B a nut N to be screwed to the bolt B is inserted, while on top and bottom of said insertion part ribs 124 are provided. In this way, because the lower sash part 20 and the door 1 can be formed as an integral unit, the mounting work of parts in the door can be remarkably improved.