PURPOSE: To increase an amount of activated carbon per a unit volume and enhance adsorbing property by using an adsorbing material which is prepared by mixing particulate activated carbon as a stock material with a binder and molding the resultant mixture into a honeycomb shape to subjected the same to drying treatment to enlarge a fine pore diameter thereof.

CONSTITUTION: Sucked air is preliminarily treated by a filter 14 to remove crude dust therein and flowed into an electrostatic dust collecting means 20 and, in passing fine particle ionized by an ionizing wire 24 through an electrostatic field, said ionized particle is collected by a collecting electrode plate 26. Hardly ionized hydrocarbon, odors, CO2 or the like are adsorbed by an adsorbing material 22 arranged to a rear stage of the electric dust collecting means 20. Said adsorbing material 22 is formed by a method wherein water and an org. binder are mixed with powdery activated carbon obtained by grinding particulate activated carbon in an appropriate amount and, after molding, the molded object is dried and, because one with a fine pore size of 14 or more formed, a particle having a particle size with a wide width is adsorbed.