PURPOSE: To reduce a cycle time in mounting parts, along with good productive yield.

CONSTITUTION: In a head unit 10, a suction head 4 having a suction nozzle 5, a video camera 8, a plane-face illumination unit made up of a panel light source 15 and a light diffusion plate 16, and a reflection mirror 14 are mounted on a mounting board 11 held by an arm 3a of a X-Y robot 3. The suction head 4 at the head unit 10 is moved downward. After an electronic part 1 at a part feeding unit 2 is clamped by the suction head 4 and moved upward, the light diffusion plate 16 is moved in a direction indicated by arrow (A). Then, the panel light source 15 is operated to illuminate the electronic part 1. Then, the image of the electronic part 1 is picked up by the video camera 8 through the reflection mirror 14. A control unit 9 calculates compensated data from the image data, and a motor 12 is rotated. Then, the X-Y robot 3 is operated to mount the electronic part 1 on the circuit board 6 by moving the suction nozzle 5 downward.