To provide an optical connector adaptor having a small number of components, and simple assembling process.

An optical connector adaptor 1 is composed of: a sleeve 3; a sleeve holder 4 having a holding portion 4c having a through hole 4d in which the sleeve is inserted, and an elastic claw portion 4e fitting and locking with an optical connector plug to be connected; a covering second sleeve holder 5 equipped with an elastic installation piece 5b having an installation projection 5a on the outside of the elastic claw portion on the sleeve holder; and an adaptor housing 2 including the sleeve holder and the covering second sleeve holder in a through-hole 2b of a housing portion 2a to be held, and connecting the optical connector plug to be connected which is inserted from both side opening portions of the through-hole of the housing portion, to the held sleeve holder and the covering second sleeve holder.