Abstract: As the third part of these series works, the present paper deals with a piezoelectric cantilever beam subjected to a transverse concentrated force at the free end. The general solutions of the electro-mechanical fields in the smart beam are obtained and discussed by use of the semi-inverse method. In order to get a solution clearly and comparably, a piezoelectric cantilever beam is considered under three different cases: without body force, with constant body force and with gradient body force.