To relieve a motor from burden at starting operation, depending on pressure in a tank.

This air compressor 10 comprises a control part 94 having operation stop means for stopping the energization of the motor 68 when the rotating speed of the motor 68 is a preset value or lower and stop means for stopping the energization of the motor 68 until the pressure in the tank is lower than a preset value when the pressure in the tank is determined to be the preset value or higher. The control part 94 therefore stops the energization of the motor 68 after determining a lack of torque due to voltage drop when the motor speed is the preset value or lower and stops the energization of the motor 68 until the pressure in the tank is lower than the preset value when the pressure in the tank is the preset value or higher, thereby preventing the unreasonable drive of the motor 68 in the state that there is sufficient pressure in the tank.