PURPOSE: To prevent firing phenomenon due to discharge as well as shorten the time of cleaning by sufficiently cleaning residual metals in a drain hose by means of a valve device provided in the line of supplying a cleaning liquid.

CONSTITUTION: As the first cleaning process, the lines 7 and 10 are connected to each other by operating a valve device 8, the line 10 is connected to a drain hose 11 by operating a three-way valve 9, and a drain sucker B is further operated to suck up waste water. As the second cleaning process, the lines 7 and 10 are connected to a paint supply system 2 by operating a valve device 8, a three-way valve 9, and a color-changing valve device 4 and then a paint pathway inside the color- changing valve device 4, the paint supply system 2, and a rotary type atomizing head 1a are cleaned. At the same time, a three-way valve 13 is operated, a drain recovery container 12 is connected to a drain hose 15, and then the sucker B is operated. As the third cleaning process, the valve device 8 is operated, the line 7 is connected to the line 14, the three-way valve 13 is operated, the line 14 is connected to the drain hose 15, and the sucker B is operated.