To realize a technique that dispenses with a negative electron affinity of a surface of a compound semiconductor when emitting a polarized electron beam from a cathode.

A multiphoton excitation type polarized electron beam generator has the cathode comprising the compound semiconductor, and a laser source for irradiating the cathode, and the wavelength of a laser beam is set from half to below the energy spread of a forbidden band of the compound semiconductor. The device excites electrons with two photons to thereby provide a large polarization even without separating the degeneracy of the energy bands of a heavy electron hole and a light electron hole, and can excite the electrons to a high energy level in a conduction band to thereby dispense with a negative electron affinity for external emission of the electrons from the compound semiconductor. With the use of a normal compound semiconductor, the device can generate a polarized electron beam stably for a long period.