A turbine generator system includes a turbine power generation unit including a generator and a turbine for driving the generator. The turbine generator system also includes an evaporator, a condenser, a medium feeding pump, a circulating pump, and a feeding passage. The evaporator receives heat from a heat source and supplies a working medium in a vapor phase containing a lubricant to the turbine power generation unit. The condenser condenses the working medium which has flowed through the turbine. The medium feeding pump raises a pressure of the condensed working medium and feeds the working medium to the evaporator, and the working medium extracted from the evaporator is supplied through the feeding passage to bearings in the turbine power generation unit.