A common body (15) of a coater unit (14) is mounted on a robot device (13). A common body gripper (33) is fixedly mounted on a fixed plate (32) of an atomizing head changing and washing device (31). At the time of replacing a used atomizing head (19') and a used paint cartridge (24') by a washed atomizing head (19) and a replenished paint cartridge (24), respectively, the common body (15) is gripped and located in a predetermined position by the common body gripper (33). When the common body (15) is gripped by the common body gripper (33), the robot device (13) is put in a reduced power mode attenuating driving forces to leave said common body (15) in a freely movable state by application of an external force.