PURPOSE: To reduce apparent contraction amount of entire legs and suppress the warp of a synthetic resin module by a method wherein the module is injection-molded so that it has a croock at the center in the lengthwise direction of a pair of side walls, which form legs spreading over a full width of a plate for mounting load.

CONSTITUTION: A synthetic resin module is injection-molded so that at the center in the lengthwise direction of a pair of side walls 4b, 4c which form a second leg 4B and a third leg 4C which spread over a full length, a full or almost full width of a plate for mounting load among three legs 4A, 4B, 4C, crooks U, T are formed which crook inward or outward. As a result, while the module is cooled under a room temperature after it is taken out from a mold, the crooks U, T are deformed so that it is stretched lengthwise of side walls 4b, 4c. Therefore, the contraction amount of the entire legs can be reduced apparently, preventing the synthetic resin module from warping in a state pro truding upward.