PROBLEM TO BE SOLVED: To identify physical quantities inside a plasma including a magnetic field distribution, an electron density distribution, and an electron temperature distribution even when the magnetic field distribution, the electron density distribution, and the electron temperature distribution inside the plasma are unknown. SOLUTION: The calculation device comprises: an acquisition part which acquires an azimuth angle and an ellipticity angle of a plane of polarization of a laser beam passing through a plasma; and a calculation part which calculates at least one of a magnetic field distribution, an electron density distribution, and an electron temperature distribution inside the plasma on the basis of the azimuth angle and the ellipticity angle. COPYRIGHT: (C)2013,JPO&INPIT