The amount of the coating disposed of at the time of a color change is reduced, and the cleaning of a coating machine body is simplified. When cleaning a coating cartridge (10), air and a cleaning fluid are supplied to a coating bag (12) in a squashed state through an upper end mouth section (12b) thereof, thereby causing the coating bag (12) to be expanded. The hydraulic fluid in a hydraulic fluid chamber (an enclosed space (14)) of the coating cartridge (10) is recovered through a hydraulic fluid evacuation passage (26) in the cartridge with the expansion of the coating bag (12). In the next process, the hydraulic fluid is supplied to the hydraulic fluid chamber (the enclosed space (14)) of the coating cartridge (10) through an in-cartridge hydraulic fluid supplying passage (22) different from the hydraulic fluid evacuation passage (26) to squash the coating bag (12), causing the cleaning fluid to be evacuated from a lower end mouth section (12c) of the coating bag (12).