PURPOSE: To reduce the number of parts and dissolve fall-off of a component by regulating excessive tightening of a bolt with a regulating part formed on the bolt, when a part to be fitted of a component made of resin or the like is fitted to a prescribed fitting place.

CONSTITUTION: In the part fitting construction in which a part 20 to be fitted is fitted between the head part seat 12a of a bolt 10 and the surface of a fitting place 30 by inserting the shaft part 14 of the bolt 10 through a bolt inserting hole 22 formed on the part 20 to be fitted of a component, a regulating part 18 regulating screwing-in of the shaft part 14 into the screw hole 32 of the fitting place 30 is formed on the shaft part 14 of the bolt 10. Together with this, the dimension between the head part seat 12a of the bolt 10 and the surface of the fitting place 30 in the condition of regulating screwing-in by the regulating part 18 is set to be larger dimension than the thickness of the part 20 to be fitted.