PURPOSE: To prevent clogging of the respective air holes by spraying the atomized flow of washing liquid from the outside of an air cap after spray in an automatic coating machine is stopped and thereafter spraying purge air through the respective air holes of the air cap and spraying flushing air from the outside.

CONSTITUTION: After coating spray operation is completed, low-pressure purge air is continuously atomized via an atomized air path 3 and a pattern regulation air path 4 of a spray gun main body 1. Then the purge air is stopped and washing liquid (mixed with air) is sprayed through a washing gun 5 from the outside of an air cap 2. Furthermore after spray of washing liquid and washing are completed, purge air is sprayed through the respective air holes of the air cap 2 in order to dry the slight washing liquid infiltrated into the inside of the air cap 2. However since the washing liquid stuck on the outer face of the air cap 2 can not be purged even when the purge air is blown out from the inside, both spray of purge air from the inside and spray of flushing air from the outside are performed in combination in a short time.