PURPOSE: To promote the formation of the atmosphere of the org. solvent vapor and to effectively prevent the stiffening of an automatic primer applying brush in the device contg. the brush.

CONSTITUTION: This device consists of a brush container 1, a stiffening preventing tank 3 adjacent to the container 1 and having an org. solvent reservoir 2, a shutter 4 for externally closing the tank 3 and a gas passage 8 connected to inject a compressed inert gas into the liq. phase in the reservoir 2. Meanwhile, the container 1 is communicated with the vapor phase in the reservoir 2 to supply the org. solvent vapor into the container 1 in the tank 3, and the vaporization of the org. solvent is promoted by the injection of the compressed inert gas in this device for preventing the stiffening of a primer applying brush.