In the present optical switching device, a reference light of a wavelength same as or in the vicinity of a wavelength of a signal light, is given from a wavelength-variable light source via each output side optical circulator to each pertinent output light path, and is propagated through each of the output light paths in a direction inverse to a propagation direction of the signal light, and passes through each optical amplifier to be sent to an optical switch module. Then, the power of the reference light which is led to each input side optical circulator from each input light path in accordance with the optical route setting by the optical switch module, is monitored by a reference light power monitor, and loss data is acquired by a control circuit using the monitoring result, so that the optical switch module is controlled in accordance with a control parameter corrected based on the loss data. Thus, it becomes possible to grasp accurately a loss characteristic of the optical switch module to perform the setting and switching of optical routes, and also, to compensate for a loss in the optical switch module while suppressing the waveform degradation of an output signal light to the minimum.