This injection molding method uses an injection molding machine for two-material molding, which comprises a first mold part that is provided with a cavity and a second mold part that is provided with a cavity and is arranged in tandem with the first mold part. This injection molding method comprises: a first molding step wherein a material is injected into the cavity of the first mold part and the material in the cavity is compressed; and a second molding step wherein a material is injected into the cavity of the second mold part. A pressure, which is generated in the second mold part by injecting the material into the cavity in the second molding step, acts on the first mold part, and a compressive force is applied to the material in the cavity in the first molding step.