A vacuum pump exhaust system , comprising: a vacuum pump having a temperature sensor unit that is configured to measure a temperature of a rotating portion in a purge gas channel; a purge gas storage that is configured to store purge gas used in the vacuum pump; and a purge gas supply unit that is configured to supply the purge gas stored in the purge gas storage to the vacuum pump and is configured to control a flow rate of the purge gas; wherein at least when the temperature sensor unit measures the temperature of the rotating portion, the purge gas supply unit is configured to supply the purge gas to the vacuum pump such that an amount of the purge gas satisfies one of following conditions: an amount of the purge gas flows at a higher velocity than a backflow velocity of gas exhausted by the vacuum pump on at least a part of a downstream side of flow of the purge gas of the temperature sensor unit, an amount of the purge gas has a pressure of one of an intermediate flow and a viscous flow around the temperature sensor unit, characterized in that the purge gas supply unit is configured to set at least two flow rates of the purge gas supplied to the vacuum pump, a first of the flow rates is set when a temperature is measured by the temperature sensor unit, and a second of the flow rates is set except when a temperature is measured by the temperature sensor unit, the first of the flow rates being greater than the second of the flow rates. a vacuum pump having a temperature sensor unit that is configured to measure a temperature of a rotating portion in a purge gas channel; a purge gas storage that is configured to store purge gas used in the vacuum pump; and a purge gas supply unit that is configured to supply the purge gas stored in the purge gas storage to the vacuum pump and is configured to control a flow rate of the purge gas; wherein at least when the temperature sensor unit measures the temperature of the rotating portion, the purge gas supply unit is configured to supply the purge gas to the vacuum pump such that an amount of the purge gas satisfies one of following conditions: an amount of the purge gas flows at a higher velocity than a backflow velocity of gas exhausted by the vacuum pump on at least a part of a downstream side of flow of the purge gas of the temperature sensor unit, an amount of the purge gas has a pressure of one of an intermediate flow and a viscous flow around the temperature sensor unit, characterized in that the purge gas supply unit is configured to set at least two flow rates of the purge gas supplied to the vacuum pump, a first of the flow rates is set when a temperature is measured by the temperature sensor unit, and a second of the flow rates is set except when a temperature is measured by the temperature sensor unit, the first of the flow rates being greater than the second of the flow rates. an amount of the purge gas flows at a higher velocity than a backflow velocity of gas exhausted by the vacuum pump on at least a part of a downstream side of flow of the purge gas of the temperature sensor unit, an amount of the purge gas has a pressure of one of an intermediate flow and a viscous flow around the temperature sensor unit, characterized in that the purge gas supply unit is configured to set at least two flow rates of the purge gas supplied to the vacuum pump, a first of the flow rates is set when a temperature is measured by the temperature sensor unit, and a second of the flow rates is set except when a temperature is measured by the temperature sensor unit, the first of the flow rates being greater than the second of the flow rates. <EOS>