PURPOSE: To contrive improvements of a fitting part by an adhesive agent and processabilities such as boring of the fitting part, by a method wherein a volume ratio of a fiber of a fitting part of a separate parts is made high or the volume ratio of the fiber of its circumference is made high and impregnation of resin is controlled.

CONSTITUTION: A tray-shaped FRP member 1 possesses a separate member fitting part 2, which is not impregnated with a resin, on its corner part. For example, a bracket 3 as separate parts is stuck to the separate member fitting part 2. On that occasion, the separate member fitting part 2 is impregnated favorably with the adhesive agent and high adhesion is obtained between both of them even if pretreatment is not performed. As for the FRP member 1, a preform is molded by a stamping technique, liquid resin is cast by an SRIM method and it is impregnated with the resin, solidified and molded.