PURPOSE: To efficiently decompose a malodorous gas or bacteria by using a base plate, on which a zinc oxide film is formed by electrolysis, for an air purifying device.

CONSTITUTION: The zinc oxide coating film is formed on the surface of the base plate by electrolysis or by oxidizing zinc on the surface by anodic oxidation process. Zinc oxide is easily fixed on the surface of the base plate by electrolysis or anodic oxidation process. Zinc oxide easily reacts with a sulfur compound as a malodor causing material deodorized thereof. Zinc oxide has sterilizing action on bacteria or fungi due to the elution of the metallic ion. Since zinc oxide is not kneaded into a coating material or a resin and directly in contact with the malodor or the bacteria over the whole film, excellent efficiency is attained. Ultraviolet rays is not necessary and the function is sufficiently exhibited even in the dark place.