The optical element is a long optical element obtained by cutting off a long main body section, which is connected to a runner section via a gate section and comprises an optical section having at least a first optical surface that transmits or reflects light, from the gate section to form an individual piece. The first optical surface has a curved surface that is curved in the short direction at least at an end in the longitudinal direction. A first edge portion of the gate section side end face of the main body section on the first optical surface side is curved, conforming to the first optical surface. The boundary surface between the main body section and the gate section is formed to be narrower than the gate section side end face of the main body section. At least the distance between the part of the first edge portion, which corresponds to the effective region of the first optical surface, and the part of a second edge portion, which is on the boundary surface on the first optical surface side and corresponds to the effective region of the first optical surface, is formed to be uniform.