PURPOSE: To obtain the compound conductive material having the stabilized resistance characteristic efficiently in a short time by applying the specified isotropic pressure to the compound conductive material, which is obtained by mixing a crystalline thermoplastic resin and conductive particles.

CONSTITUTION: Crystalline thermoplastic resin made of polyolefin group resin and conductive particles made of carbon black particles are kneaded by using a high temperature kneader, and thereafter, it is formed into a desired shape to generate the compound conductive material. Isotropic pressure at 100kg/cm2.G or more is applied to this compound conductive material by using an isotropic pressure applying device to perform the pressure treatment. Volume of the whole the compound conductive material is thereby reduced in response to the applied pressured to stabilize the resistance characteristic. As a result, the compound conductive material, which has the stabilized resistance against the long term use with a heat cycle and an electrifying cycle, efficiently in a short time.