Abstract: To provide a reflected light measurement device capable of efficiently performing disconnection inspection on an optical connector, and a plurality of optical fibers. The reflected light measurement device 1 includes a laser light source 2, a beam splitter 3 that branches measurement laser light L into measurement laser light L1 to be transmitted and reference laser light L2 to be reflected, a reference mirror 4 including an optical path length varying mechanism capable of adjusting an optical path length of the reference laser light L2, an optical path length switching unit 5, and switches the optical path length of the reference laser light L2 to a plurality of fixed lengths, and a photometer 6 that receives measurement laser light L1? reflected at defect sites D1 and D2 such as disconnection inside connectors C1 and C2, and reference laser light L2? reflected by the reference mirror 4.