A ventilation blower comprising: an inverter main circuit including a plurality of switching elements (31 to 36) to be switched to convert direct-current power into three-phase alternating-current power; a motor body including a stator and a rotor and to be driven by the inverter main circuit; a motor control circuit to control the inverter main circuit; and a storage device (16;43), wherein the storage device is adapted to store an angular velocity of the rotor and a torque current value at a first operation point at which to obtain a first air volume on a first load characteristic, and the angular velocity and the torque current value at a second operation point at which to obtain a second air volume on the first load characteristic, the second air volume being different from the first air volume, the motor control circuit is adapted to calculate, from the angular velocity and the torque current value at the first operation point and the angular velocity and the torque current value at the second operation point, the angular velocity and the torque current value at a third operation point at which to obtain a third air volume on the first load characteristic, and the motor control circuit is adapted to cause the inverter main circuit to drive the motor body with the angular velocity and the torque current value at the third operation point, wherein the storage device is configured to store the angular velocity and the torque current value at a fourth operation point at which to obtain the first air volume on a second load characteristic different from the first load characteristic, and the angular velocity and the torque current value at a fifth operation point at which to obtain the second air volume on the second load characteristic, and wherein the motor control circuit is configured to calculate, from the angular velocity and the torque current value at the fourth operation point and the angular velocity and the torque current value at the fifth operation point, the angular velocity and the torque current value at a sixth operation point at which to obtain the third air volume on the second load characteristic, and obtains, from the angular velocity and the torque current value at the third operation point and the angular velocity and the torque current value at the sixth operation point, an air volume characteristic that indicates a relationship between the angular velocity and the torque current value at the third air volume. an inverter main circuit including a plurality of switching elements (31 to 36) to be switched to convert direct-current power into three-phase alternating-current power; a motor body including a stator and a rotor and to be driven by the inverter main circuit; a motor control circuit to control the inverter main circuit; and a storage device (16;43), wherein the storage device is adapted to store an angular velocity of the rotor and a torque current value at a first operation point at which to obtain a first air volume on a first load characteristic, and the angular velocity and the torque current value at a second operation point at which to obtain a second air volume on the first load characteristic, the second air volume being different from the first air volume, the motor control circuit is adapted to calculate, from the angular velocity and the torque current value at the first operation point and the angular velocity and the torque current value at the second operation point, the angular velocity and the torque current value at a third operation point at which to obtain a third air volume on the first load characteristic, and the motor control circuit is adapted to cause the inverter main circuit to drive the motor body with the angular velocity and the torque current value at the third operation point, wherein the storage device is configured to store the angular velocity and the torque current value at a fourth operation point at which to obtain the first air volume on a second load characteristic different from the first load characteristic, and the angular velocity and the torque current value at a fifth operation point at which to obtain the second air volume on the second load characteristic, and wherein the motor control circuit is configured to calculate, from the angular velocity and the torque current value at the fourth operation point and the angular velocity and the torque current value at the fifth operation point, the angular velocity and the torque current value at a sixth operation point at which to obtain the third air volume on the second load characteristic, and obtains, from the angular velocity and the torque current value at the third operation point and the angular velocity and the torque current value at the sixth operation point, an air volume characteristic that indicates a relationship between the angular velocity and the torque current value at the third air volume.