A steam turbine system (200) includes a steam turbine (60) in which a main flow path (C) through which a main steam flows is formed, and a saturated steam generation portion (210) that is configured to generate a saturated steam. The saturated steam generation portion (210) is configured to feed the saturated steam into a wet region (C1) in which the main steam in the main flow path (C) is in a wet state via a hollow portion formed inside a stator vane (650) of the steam turbine (60). The stator vane (650) has a plurality of supply ports that are formed such that the hollow portion is configured to communicate with the main flow path (C), and a discharge amount of the saturated steam increases from an inner circumferential side toward an outer circumferential side in a blade height direction.