A pump device, comprising: a pump main body (10, 20, 30) including a discharge port, a suction port, a pump chamber that is communicable with each of the discharge port and the suction port, a movable member that alternately suctions gas into the pump chamber and discharges gas from the pump chamber, and a drive unit including a motor that drives the movable member and is capable of changing a flow rate of gas discharged from the discharge port according to a rotation speed; characterized in that the pump device further comprises: a temperature sensor that is attached to the pump main body (10, 20, 30) and measures a temperature of the pump main body (10, 20, 30), to thereby output a temperature signal relating to a temperature of the gas; and a controller including an input unit (51, 52, 53) into which an external signal for specifying a reference flow rate of the gas discharged from the discharge port is input, an arithmetic unit that calculates, based on the temperature signal, a density change amount of the gas to obtain an actual flow rate of the gas discharged from the discharge port, an output unit that outputs a correction signal for correcting a rotation speed of the motor such that the actual flow rate equals the reference flow rate, and a storage unit that stores a correction coefficient including a temperature characteristic of the pump main body (10, 20, 30), which are obtained in advance, wherein the arithmetic unit calculates the actual flow rate of the gas by multiplying the reference flow rate by each of the density change amount and the correction coefficient. a pump main body (10, 20, 30) including a discharge port, a suction port, a pump chamber that is communicable with each of the discharge port and the suction port, a movable member that alternately suctions gas into the pump chamber and discharges gas from the pump chamber, and a drive unit including a motor that drives the movable member and is capable of changing a flow rate of gas discharged from the discharge port according to a rotation speed; characterized in that the pump device further comprises: a temperature sensor that is attached to the pump main body (10, 20, 30) and measures a temperature of the pump main body (10, 20, 30), to thereby output a temperature signal relating to a temperature of the gas; and a controller including an input unit (51, 52, 53) into which an external signal for specifying a reference flow rate of the gas discharged from the discharge port is input, an arithmetic unit that calculates, based on the temperature signal, a density change amount of the gas to obtain an actual flow rate of the gas discharged from the discharge port, an output unit that outputs a correction signal for correcting a rotation speed of the motor such that the actual flow rate equals the reference flow rate, and a storage unit that stores a correction coefficient including a temperature characteristic of the pump main body (10, 20, 30), which are obtained in advance, a temperature sensor that is attached to the pump main body (10, 20, 30) and measures a temperature of the pump main body (10, 20, 30), to thereby output a temperature signal relating to a temperature of the gas; and a controller including an input unit (51, 52, 53) into which an external signal for specifying a reference flow rate of the gas discharged from the discharge port is input, an arithmetic unit that calculates, based on the temperature signal, a density change amount of the gas to obtain an actual flow rate of the gas discharged from the discharge port, an output unit that outputs a correction signal for correcting a rotation speed of the motor such that the actual flow rate equals the reference flow rate, and a storage unit that stores a correction coefficient including a temperature characteristic of the pump main body (10, 20, 30), which are obtained in advance,