PURPOSE: To perform aging in a short time and uniformly by heating a thermosetting resin molding material by means of microwave.

CONSTITUTION: As a thermosetting resin molding material, a product prepd. by mixing such a thermosetting resin as an epoxy resin and a phenol resin with an inorg. filler such as a glass fiber, can be used. Aging is performed by placing the thermosetting resin molding material in a microwave heating apparatus and irradiating the material with a microwave. When the material is irradiated with a microwave, molecules constituting the thermosetting resin molding material generate rotational and vibrational movements and they are heated by generating frictional heat. The whole thermosetting resin molding material can be uniformly heated by generating heat from both inside and outside caused by microwave heating. It is therefore possible to age both the surface and the central part of the thermosetting resin molding material under the same heating condition and to age uniformly the material. In addition, as it is possible to age uniformly it, it is possible thereby to shorten aging time by setting heating temp. at 50°C or higher.