To separate each polarized light of a polarization multiple signal light in which orthogonal polarized waves with the same wavelength are multiplexed, and to evaluate the characteristics of each signal light.

Rays of light made incident on a light incidence part 21 and transmitted through a variable wavelength optical filter 22 are received by a pre-processing part 23 and subjected to change of a polarization state and conversion from phase change to amplitude change. The rays of light are made incident on a polarization beam splitter 26, and the strength of one polarization component separated by the polarization beam splitter 26 is detected by a first light reception part 30, and the strength of the other polarization component is detected by a second light reception part 31. Also, both the separated polarization components are made incident on a differential balance type third light reception part 33, and the strength of a difference signal between both polarization components is detected, and the amplitude of the difference signal is detected by an amplitude detection part 34. An evaluation processing part 40 receives outputs of the first light reception part 30, the second light reception part 31, and the amplitude detection part 34 while controlling the variable wavelength optical filter 22 and the pre-processing part 23, and searches for characteristics necessary for evaluation of the polarization multiple signal light made incident on the light incidence part 21.