The optical adapter includes a first housing 3, a second housing 5, and a sleeve 7. The first housing 3 includes a connector holding part 31, a first holder portion 33, an alignment part 35, and coupling portions 36. The first holder portion 33 is integrally formed with the connector holding part 31. The alignment part 35 includes an alignment part main body 351, a second holder portion 352 integrally formed with the alignment part main body 351, and a plurality of guide portions 352, 354, and 355, integrally formed with the alignment part main body 351. Protrusion-shaped coupling portions 36 for coupling the connector holding part 31 and the alignment part 35 are integrally formed with one of the connector holding part 31 and the alignment part main body 35.