A turbine protection device provided in a steam turbine system, the steam turbine system comprising: a turbine driven by steam generated in a boiler; a condenser to condense the steam exhausted from the turbine into a condensate; a deaerator to store the condensate which is prepared by being heated and deaerated; an inlet tube to take the extraction steam for heating and deaerating into the deaerator; and a check valve provided in the inlet tube, comprising: a pressure gauge to measure a pressure of the extraction steam and a pressure within the deaerator; the turbine protection device characterized in further comprising: a shutdown valve device provided in the inlet tube and between the check valve and the deaerator; and a control unit to control the shutdown valve device using commands based on the pressure of the extraction steam and the pressure within the deaerator, wherein the shutdown valve device is opened and closed by the commands from the control unit, and when the shutdown valve device is closed, the shutdown valve device interrupts the steam flowing from the deaerator to the turbine; wherein the control unit is configured to send commands to the shutdown valve device so as to close the shutdown valve device when a condition that a differential pressure resulted from subtracting the pressure of the extraction steam from the pressure within the deaerator becomes equal to or greater than a first predetermined value, which is set in advance, continues for a predetermined time period, and send commands to the shutdown valve device so as to open the shutdown valve device when a condition that the differential pressure becomes equal to or less than a second predetermined value, which is set in advance, continues for a predetermined time period. a turbine driven by steam generated in a boiler; a condenser to condense the steam exhausted from the turbine into a condensate; a deaerator to store the condensate which is prepared by being heated and deaerated; an inlet tube to take the extraction steam for heating and deaerating into the deaerator; and a check valve provided in the inlet tube, comprising: a pressure gauge to measure a pressure of the extraction steam and a pressure within the deaerator; the turbine protection device characterized in further comprising: a shutdown valve device provided in the inlet tube and between the check valve and the deaerator; and a control unit to control the shutdown valve device using commands based on the pressure of the extraction steam and the pressure within the deaerator, wherein the shutdown valve device is opened and closed by the commands from the control unit, and when the shutdown valve device is closed, the shutdown valve device interrupts the steam flowing from the deaerator to the turbine; wherein the control unit is configured to send commands to the shutdown valve device so as to close the shutdown valve device when a condition that a differential pressure resulted from subtracting the pressure of the extraction steam from the pressure within the deaerator becomes equal to or greater than a first predetermined value, which is set in advance, continues for a predetermined time period, and send commands to the shutdown valve device so as to open the shutdown valve device when a condition that the differential pressure becomes equal to or less than a second predetermined value, which is set in advance, continues for a predetermined time period. a pressure gauge to measure a pressure of the extraction steam and a pressure within the deaerator; the turbine protection device characterized in further comprising: a shutdown valve device provided in the inlet tube and between the check valve and the deaerator; and a control unit to control the shutdown valve device using commands based on the pressure of the extraction steam and the pressure within the deaerator, a shutdown valve device provided in the inlet tube and between the check valve and the deaerator; and a control unit to control the shutdown valve device using commands based on the pressure of the extraction steam and the pressure within the deaerator, wherein the shutdown valve device is opened and closed by the commands from the control unit, and when the shutdown valve device is closed, the shutdown valve device interrupts the steam flowing from the deaerator to the turbine; wherein the control unit is configured to send commands to the shutdown valve device so as to close the shutdown valve device when a condition that a differential pressure resulted from subtracting the pressure of the extraction steam from the pressure within the deaerator becomes equal to or greater than a first predetermined value, which is set in advance, continues for a predetermined time period, and send commands to the shutdown valve device so as to open the shutdown valve device when a condition that the differential pressure becomes equal to or less than a second predetermined value, which is set in advance, continues for a predetermined time period.