To provide a variable optical delay line apparatus 1 in which an optical signal is delayed with a variable amount of delay.

A pair of optical fiber arrays A1 and A2, which have: an end face; an optical fiber for input/output, of which an end face works as an input/output end of an optical signal and the cross section of the other end is arranged at the aforementioned end face; and an optical fiber for delay whose cross section of both ends are arranged at the aforementioned end face, respectively, are so arranged that the respective end faces are facing to each other. The combination of the cross sections of the optical fibers which are optically connected between the end faces of the pair of optical fiber arrays is switched, and the optical path between the respective input/output ends of the pair of the optical fiber arrays is switched. Thus the amount of delay of the optical signal transmitted in the optical path is switched.