disclosed is an alkali metal thermoelectric power generator comprising a plurality of thermoelectric converters , which are connected in electrical series to one another by an external electronic conductor device , each of the converters converting thermal energy into electrical energy by utilizing the phenomenon that an alkali metal , arranged on each side of a solid electrolyte , diffuses across the electrolyte if the density thereof on one side of the electrolyte differs from that on the other side of the same . the generator further comprises a piping consisting of a plurality of connection pipes for returning the alkali metal condensed in a second spatial region of each thermoelectric converter to a first spatial region thereof through a common pump . further , the respective open ends of the connection pipes , which connect the respective first regions of the converters to one another , are positioned in those portions of the respective first regions where only the vapor phase alkali metal exists .