PROBLEM TO BE SOLVED: To provide a method for the blow diffusion of chemicals capable of getting sufficient chemical effect over a wide area. SOLUTION: A pipe 2 of a chemicals blow-diffusion apparatus 1 is continuously placed around the objective treating area A and air containing chemicals is blasted from nearly the whole length of the pipe 2 to diffuse the chemicals-containing air to the objective treating area and achieve sufficient effect of chemicals even on a wide treating area A. COPYRIGHT: (C)2008,JPO&INPIT