[Problem to be Solved]There is provided an optical transmission device in wavelength-division-multiplexing-based optical communications that has both of improved reliability because of provision of backup optical transceiving unit and power saving capability because of appropriate control.[Solution]An optical transmission device is configured with optical switch means 40, a plurality of optical transceiving means 41 and control means 42. The optical switch means 40 outputs an input optical signal to a given path. Each optical transceiving means 41 receives an optical signal from the optical switch means 40 and transmits an optical signal to the optical switch means 40. The control means 42 performs various kinds of control. The optical transceiving means 41 operates in three operation states: a normal mode in which the optical transceiving means transmits and receives optical signals, a first standby mode which is a standby state, and a second standby mode in which power consumption is smaller than power consumption in the first standby mode. The control means 42 includes means for causing the optical transceiving means in the first standby mode to transition to the normal mode and causes the optical transceiving means in the second standby mode to transition to the first standby mode or the normal mode.