An RTM molding device (100, 200), comprising: a molding die (1, 21) inside which a cavity is formed, a resin injection line (2, 22) and a suction line (3, 23) that are connected to the cavity, a surface molding layer (4, 24), and a resin diffusion portion, the device being configured such that a fiber-reinforced base material (11, 31) is placed in the cavity, pressure inside the cavity is reduced, and a resin composition is injected into the cavity to impregnate the fiber-reinforced base material (11, 31) and form a molded body, wherein the surface molding layer (4, 24), which is disposed between the fiber-reinforced base material (11, 31) and the molding die (1, 21), has a plurality of through-holes formed therein, and has sufficient rigidity that the thickness does not substantially change under a pressure inside the cavity when the inside of the cavity is placed under reduced pressure to perform resin impregnation, and the resin diffusion portion, which is located on a side of the surface molding layer (4, 24) opposite the fiber-reinforced base material (11, 31), and comprises a resin flow path formed so as to connect with the plurality of through-holes of the surface molding layer (4, 24), are provided on at least one surface of the fiber-reinforced base material (11, 31), wherein the resin diffusion portion is composed of at least one resin diffusion layer (8a, 8b, 28), which has a plurality of through-holes (9, 10) formed therein, the through-holes (9, 10) having a larger diameter than the through-holes formed in an adjacent layer on a side of the fiber-reinforced base material (11, 31), has sufficient rigidity that the thickness does not substantially change under the pressure, and is disposed between the surface molding layer (4, 24) and the molding die (1, 21), and the through-holes (9, 10) formed in each layer connect with the through-holes formed in an adjacent layer to form a resin flow path, wherein the surface molding layer (4, 24) is a porous plate formed from a punched metal, and wherein the resin diffusion layer (8a, 8b, 28) is a porous plate formed from a punched metal. a molding die (1, 21) inside which a cavity is formed, a resin injection line (2, 22) and a suction line (3, 23) that are connected to the cavity, a surface molding layer (4, 24), and a resin diffusion portion, the device being configured such that a fiber-reinforced base material (11, 31) is placed in the cavity, pressure inside the cavity is reduced, and a resin composition is injected into the cavity to impregnate the fiber-reinforced base material (11, 31) and form a molded body, wherein the surface molding layer (4, 24), which is disposed between the fiber-reinforced base material (11, 31) and the molding die (1, 21), has a plurality of through-holes formed therein, and has sufficient rigidity that the thickness does not substantially change under a pressure inside the cavity when the inside of the cavity is placed under reduced pressure to perform resin impregnation, and the resin diffusion portion, which is located on a side of the surface molding layer (4, 24) opposite the fiber-reinforced base material (11, 31), and comprises a resin flow path formed so as to connect with the plurality of through-holes of the surface molding layer (4, 24), are provided on at least one surface of the fiber-reinforced base material (11, 31), wherein the resin diffusion portion is composed of at least one resin diffusion layer (8a, 8b, 28), which has a plurality of through-holes (9, 10) formed therein, the through-holes (9, 10) having a larger diameter than the through-holes formed in an adjacent layer on a side of the fiber-reinforced base material (11, 31), has sufficient rigidity that the thickness does not substantially change under the pressure, and is disposed between the surface molding layer (4, 24) and the molding die (1, 21), and the through-holes (9, 10) formed in each layer connect with the through-holes formed in an adjacent layer to form a resin flow path, wherein the surface molding layer (4, 24) is a porous plate formed from a punched metal, and wherein the resin diffusion layer (8a, 8b, 28) is a porous plate formed from a punched metal.