To improve both optical coupling efficiency and insulation between a light-emitting element and a light-receiving element, in an optical coupler having a structure wherein light emitted from the light-emitting element is reflected on a reflecting surface and then received by the light-receiving element.

The light-emitting element 34 and the light-receiving element 35 are sealed by a primary mold part 38 having translucency, and the surface of the primary mold part 38 is covered with a secondary mold part 39 having a refractive index lower than the primary mold part 38. The primary mold part 38 serves as (a part of) a spheroid. The light-emitting element 34 is positioned on the side further distant than one focal point A1 in the long axis direction of the spheroid from the center O of the spheroid. The light-receiving element 35 is also positioned on the side further distant than the other focal point A2 in the long axis direction of the spheroid from the center O of the spheroid.