The invention discloses a device utilizing an adjustable wave length laser to carry out a magneto-optical ellipsometry test and a measuring method, and belongs to the technical field of generalized ellipsometry measurement. The device comprises a laser power supply, the adjustable wave length laser, a light path system, an electromagnet, a lock-in amplifier and a PC (personal computer) machine, wherein the light path system comprises a polarizer, two diaphragms, a chopper, a polarization analyzer, a collecting lens, an optical filter and a photoelectric detector and the like; the device is characterized in that a single wave length magneto-optic ellipsometry test extends to multi-wave-length magneto-optic test through the combination of the adjustable wave length laser and a magneto-optic ellipsometry system; the laser can send laser lights with different frequency through regulating the electric current of the laser power supply, meanwhile, the optical filter which is connected to the photoelectric detector in a pre-position manner and corresponds to the emergent laser light frequency, is replaced, the PC machine can carry out a multi-wave-length magneto-optic test on a magnetic material sample, and the curve of a spectrum of a magneto-optic coupling coefficient is obtained. The device provided by the invention has the advantages that the structure is simple and reasonable, the assembly is convenient, the measurement accuracy is high, and the operation is simple.