Provided are an electron emitter continuously emitting electrons stably even in the atmosphere, a charger using the electron emitter, and a charging method using the charger. The electron emitter includes a electron emitting element consisting of a first electrode, a second electrode, and a semiconductor layer formed therebetween, and a power supply for alternately applying a positive voltage enabling electron emission and a negative voltage having a polarity opposite to the positive voltage. At least a part of the surface on the first electrode side of the semiconductor layer is formed of a porous semiconductor layer. Electrons captured in the porous semiconductor layer in the course of electron emission with application of a positive voltage disturb electron emission from the electron emitting element. Such electrons, however, are removed by application of a negative voltage.