An optical crossconect device comprises an optical switch, input optical level monitoring unit for monitoring optical levels of optical signals supplied to there to, signal generating unit for generating a monitoring signal to monitor the optical switch, input optical signal selecting unit for selecting the monitoring signal generated by the monitoring signal generating unit provided between the optical transmission signal input unit and the optical switch and for supplying the selected optical signal to the optical switch, and input optical signal controlling unit for controlling the input optical signal selecting unit based on an output of the input optical level monitoring unit.