A method of using the Thomson scattering of a CO2 laser beam is proposed to measure the poloidal magnetic field produced by the plasma current in diffuse toroidal pinches of the Tokamak type. The method is based on resolving the relative shape of the cyclotron lines, whose broadening is introduced by "misalignment" due to the poloidal field with respect to the large toroidal magnetic field on which the scattering system is aligned. A small improvement in currently available transversely excited atmospheric CO2 lasers is necessary to perform the measurement.