A photoemission electron microscopy having a light source system for carrying out a high-resolution measurement such as work function distribution measurement or magnetic domain distribution with reliability, and a high-sensitivity measurement method using the photoemission electron microscopy. A photoemission electron microscopy having an excitation light source system in which a specimen is irradiated with irradiation light from a light source uses a vacuum chamber in which the specimen is placed and an objective lens which collects the irradiation light on a specimen surface. The objective lens is accommodated in the vacuum chamber. The light source may be placed outside the vacuum chamber. A condenser lens which makes the irradiation light from the light source generally parallel may be placed between the light source and the vacuum chamber. A transmission window which transmits the irradiation light while the vacuum chamber is sealed may be placed between the condenser lens and the objective lens. If a diffraction grating for selecting the wavelength of the irradiation light or a polarizing filter for selecting the direction of circularly polarized light in the irradiation light is used between the condenser lens and the transmission window, a high-resolution measurement of a work function distribution or a magnetic domain distribution on the specimen surface can be carried out.