A method for molding a composite material and a device for molding a composite material are provided which are able to suppress the occurrence of voids in a composite material and improve the mechanical characteristics and appearance quality of the composite material. In the method for molding a composite material (10), a seal region (270) including a cavity (250) in which a reinforcing base material (11) is disposed and an outer peripheral region (260) that communicates with an outer periphery of the cavity is air-tightly sealed by means of a first sealing member (310). Then, an operation of suctioning a gas from the outer peripheral region to evacuate the gas in the seal region is started, and a resin (12) is injected into a part of the cavity. Next, a mold (200) is clamped to provide a liquid-tight seal between the cavity and the outer peripheral region by means of a second sealing member (320) while pressing the resin to fill the cavity with the resin. After that, the operation of suctioning the gas from the outer peripheral region is stopped.