Accurate evaluation of the P,T-odd Faraday effect (rotation of the polarization plane for the light propagating through a medium in presence of an external electric field) is presented. This effect can arise only due to the P,T-odd (P - space parity, T - time reflection) interactions and is different from the ordinary Faraday effect, i.e., the light polarization plane rotation in an external magnetic field. The rotation angle is evaluated for the intracavity absorption spectroscopy- type experiments with Xe and Hg atoms. The results show that the Hg atom may become a good candidate for a search for the P,T-odd effects in atomic physics.