Subject of study. The paper describes the development of an optical radiation polarization analyzer for the Tachomag, a space-based solar spectromagnetograph for the International Space Station. This is the third paper in a series of articles devoted to the development of a solar magnetograph planned for deployment on the Russian segment of the International Space Station. The first two articles of the series, published earlier in this journal, described a solar telescope and an optical diffraction spectrograph, which are also components of the Tachomag, the spectromagnetograph developed for the International Space Station. Aim of study. This study developed a parallel-type polarization analyzer for the Tachomag with the necessary resolution and accuracy to measure all the components of the Stokes vector in selected spectral lines as well as the speed required to study the dynamics of fast processes in the solar photosphere. Method. This paper, for the first time, presents a polarization analyzer for a space solar magnetograph, which operates on the principle of simultaneous data acquisition under all polarizations. The characteristic features of the device include the absence of traditional polarization modulators in the composition as well as small dimensions and weight characteristics, which are particularly important for space devices. Main results. We determined that even the space version of the parallel polarization analyzer provided spectrum imaging under various polarizations with the required angular resolution of 0.35′′ according to the Rayleigh criterion in a field of view of 5′, along with a spectral resolution of 30 mÅ in a range of 2.52 Å, which corresponded to the characteristics of the solar optical telescope and spectrograph of the Tachomag. Practical significance. The development of the Tachomag as a spectromagnetograph for the International Space Station will aid the mitigation of several urgent issues in solar and plasma physics and will create a reserve for preparing for future complex missions related to solar research from close distances.