To provide an optical isolator module capable of realizing the reduction of mounting cost by reducing the time required for aligning an optical axis at assembling.

In the optical isolator module, the principal part of an optical isolator is constituted of a 1st double refraction crystal 8, a Faraday rotator 9, a half wavelength plate 10 and a 2nd double refraction crystal 11 arranged in order from a semiconductor element side, and the optical isolator module is constituted so that the displacement amount from the optical axis of an incident light caused by two double refraction crystals may compensate the displacement amount from the optical axis of the light beam caused by the refraction of optical devices other than the double refraction crystals constituting the optical isolator.