In the photocathode, an underlayer made of a crystalline material containing La2O3 is provided between a supporting substrate and a photoelectron emission layer, and is in contact with the photoelectron emission layer. Therefore, for example, at the time of heat treatment in a manufacturing process of the photocathode, dispersion to the supporting substrate side of an alkali metal contained in the photoelectron emission layer is suppressed. Further, it is assumed that this underlayer functions so as to reverse the direction of, out of photoelectrons e— generated within the photoelectron emission layer, photoelectrons traveling toward the supporting substrate side to the side opposite thereto.