Abstract: Disclosed is an optical switch of the rotary-type in which a pair of opposing optical transmission path mounting members are disposed on the same axis.A plurality of junction faces of optical transmission paths disposed on the respective opposing plane portions of the mounting members along phantom circles which are opposite to each other and concentric with the pair of mounting members respectively with respect to the axis so that the junction faces on the respective plane portions are capable of being correspondingly opposite to each other.When the pair of the mounting members are relatively rotated about the axis, the facing mates of the opposing junction faces of the optical transmission paths are changed over to switch the optical transmission paths.In the case where an optical path relay member is interposed between the pair of the optical transmission path mounting members, the optical transmission paths can be switched by only the rotation of the optical path relay member.