The purpose of the present invention is to provide a production method of a composite material that increases interlayer strength. In this composite material production method, multiple prepregs (10) formed by impregnating a fiber reinforced substrate with an uncured matrix resin are laminated and thermoformed. Prepregs (10) are used that comprise a void layer (12) that does not contain resin and that is continuous in the in-plane direction, and resin layers (11a, 11b) that are arranged on both sides of the void layer; short fibers (13) are arranged on the facing surfaces of a prepreg (10) and a prepreg (10) adjacent to each other, and thermoforming is performed after degassing the void layer (12) by evacuating the laminated prepregs (10).