PURPOSE: To provide a composite resin blank for molding used for novel resin treatment, in which treatment is conducted by utilizing the pressure of a gas generated on the inside by heating, and to obtain high usefulness when various molded forms are produced in a small scale by reducing large-sized expensive molding facilities in the composite resin blank for molding in this invention.

CONSTITUTION: A composite resin blank (4) for molding used for conducting treatment by utilizing the pressure of a gas generated on the inside by heating is composed of a gas generator (2) changed into the gas by heating or generating the gas and a resin (1), and the gas generator (2) is buried into the resin without being exposed on the surface of the resin (1).