An optical semiconductor device of one embodiment includes: a first semiconductor layer of a first conductivity type; an active layer provided on the first semiconductor layer and has a ring- or disk-like shape; a second semiconductor layer of a second conductivity type that is provided on the active layer and has a ring- or disk-like shape; a first electrode provided on the first semiconductor layer; and a second electrode provided on the second semiconductor layer. The first semiconductor layer includes a first region having a ring- or disk-like shape, and a second region provided around the outer circumference of the first region and has a smaller thickness than the first region. The first electrode is provided on the second region, and a groove or holes are provided in a portion of the second region located between the first region and the first electrode.