PURPOSE: To provide a uniform phosphor coating film with no bubble unevenness by furnishing a sub-vessel between a collection pan and a slurry supplying machine, and returning surplus slurry having got rid of bubbles back to the slurry supplying machine.

CONSTITUTION: Phosphor slurry 4 injected to the inner surface of a panel 1 is shaked off by high speed revolutions, and this shaked-off slurry 4 is collected to a sub-vessel 7 to then be fed to a phosphor slurry supplying machine 10 automatically. Thus the surplus slurry 4 is used again. Therein the surplus slurry 4 shaked off runs against the side wall of a collection pan 5 to generate bubbles 6. This surplus slurry 4 including bubbles is collected to the sub-vessel 7, and the bubbles 6 are rising afloat with passage of time. The surplus slurry 4 in the sub-vessel 7 having got rid of bubbles is fed to the slurry supplying machine 10 with on/off operation of a solenoid valve 9 actuated by a level sensor 8. This eliminates generation of bubbles unevenness when a phosphor slurry coating film is formed.