There are provided a part fixing structure and a part fixing method to a resin-made fuel tank which can firmly fix a part to a tank wall without the need of providing a molding die with a convex portion and a recess. A part fixing method for fixing a tank-associated part to a tank wall of a resin-made fuel tank, the part being formed together with a pair of hook portions, the method comprising a step of burying the hook portions in the tank wall in a melted state when the resin-made fuel tank is molded, thereby fixing the part to the tank wall after the tank wall is cooled. In order to cause the resin of the tank wall to flow well, a chevron portion having a pair of first inclined faces is projectingly provided at the bottom face of the part between the hook portions, and a second inclined face which is inclined in a direction opposite to the buried direction toward the tip of the hook portion is formed at the bottom face of each hook portion.