A metal mold including: a first inner metal mold which forms a first lens surface and a first flat surface portion of a lens; a first outer metal mold which forms a second flat surface portion; a second inner metal mold which forms a second lens surface and a third flat surface portion; and a second outer metal mold which forms a fourth flat surface portion, and wherein a first protruded portion which forms a first concaved portion on the lens is formed all around an outer periphery of the first inner metal mold, the first concaved portion serving as clearance for a burr, and a second protruded portion which forms a second concaved portion on the lens is formed all around an outer periphery of the second inner metal mold, the second concaved portion serving as clearance for a burr.