A thermoelectric generator has a heat conducting body that exchanges heat with the environment according to environmental temperature changes, a heat storing body, and a thermoelectric conversion unit and thermal resistance body arranged between the heat conducting body and the heat storing body. One end of the thermal resistance body and one end of the thermoelectric conversion unit are in contact with each other. The other end of the thermal resistance body is in contact with the heat conducting body, and the other end of the thermoelectric conversion unit is in contact with the heat storing body. The surface of the heat storing body is covered by a covering layer having certain heat insulation properties. The temperature difference generated between the heat conducting body and the heat storing body is utilized to extract electric energy from the thermoelectric conversion unit.