A wind power generating system includes: a wind mill, an induction rotating machine coupled to a rotating shaft of the wind mill; a power converting device that supplies exciting current to the induction rotating machine; a heat medium circulating structure that circulates a heat medium that receives heat generated by the induction rotating machine; a heat accumulator that accumulates heat of the heat medium; a thermal power generator that converts, into electric power, the heat of the heat medium accumulated in the heat accumulator; and an armature control unit that controls the exciting current in accordance with electric power demand of an electric power system. The armature control unit performs one or both of power generation mode control in which the induction rotating machine is operated as a power generator and heat generation mode control in which the induction rotating machine is operated as a heat generator.