A two-color laser polarimeter on large tokamaks such as ITER has been proposed for electron density measurement based on the midplane Faraday rotation. The two-color scheme in the polarimeter eliminates the Faraday rotation at vacuum windows from measured polarization angles. TwoCO2lasers which have different wavelengths of 10.6 and 9.27 &mgr;m are favorable as light sources of the two-color laser polarimeter for large tokamaks. A couple of photoelastatic modulators are used for stable polarization measurement even though the intensity and the propagation axis of an incident laser beam are changed. ©1997 American Institute of Physics.