An object of the present invention is to reduce an adverse effect of an atmosphere in a heat treatment device used in the production of an electronic device, on the characteristics of the produced electronic device. This object can be attained by covering an inner surface of the heat treatment device with an oxide passive film and bringing the surface roughness of the inner surface to not more than 1 [mu]m in terms of central mean roughness Ra. According to this heat treatment device, in curing a heat curable resin, a deterioration in the heat curable resin, for example, by decomposition or dissociation of the heat curable resin can be reduced.