PURPOSE: To eliminate spray irregularity of a powder sprayed to printing paper and to enhance workability in subsequent processes, by detecting the running speed of a body to be sprayed to control the number of rotations of a spray electromotor on the basis of a speed reference signal.

CONSTITUTION: The running speed of printing paper 9 is detected by a yard meter 12 and outputted to a sequencer 14 from a photoelectric switch 13. The sequencer 14 allows either one of inverter controlling relays 151W158 to operate and outputs a speed reference signal Sa to an inverter 10 by either one of inverter controls 161W168. The inverter 10 converts the output from a power source 11 to power on the basis of the speed reference signal Sa to control the number of rotations of a spray electromotor 1. Then, a powder is fed to a conduit 7 from a powder container 2 in the quantity equivalent to the number of rotations of the electromotor 1 through a temporary powder receiving container 6 and a proper amount of the powder is sprayed to the surface of the printing paper 9 from a spray nozzle 8 according to the running speed of the printing paper 9.