To compensate errors on robot action of a measured flow value measured by a flowmeter mounted on an arm.

On a coating robot 11, a coating material feeding pump 25 and a flowmeter 26 of a second arm are mounted. When the position, speed, and acceleration of the second arm is changed by action thereof, measurement errors are encountered. Consequently, the measured value of the flowmeter 26 is subjected to correcting calculation by a flow compensator 45 to output a corrected flow measured value to a robot controller 20. The robot controller 20 controls the revolution of a servomotor 42 of the feeding pump 25 based on the corrected flow measured value. In this way, since the coating robot 11 can feed a preset object flow rate Vr to a spray gun 18 irrespectively of the action direction, speed, and acceleration of the second arm on which the flowmeter 26 is mounted, coating can be performed so that a coating film on a surface to be coated is uniformalized.