PURPOSE: To enable to titled device to perform a photoresist treatment in a quick and effective manner by a method wherein the material to be treated is dipped in the treatment solution in which bubbles of treatment gas are formed.

CONSTITUTION: Gas 6 is flowed into a porous bubbler 3 provided at the bottom part of a treatment vessel 1 from a pipe 7, and very fine bubbles of the gas 6 formed on the surface of the bubbler 3 spreads uniformly in the treatment vessel 1. The wafer 9 housed in the cassette 10 retained in a conveying mechanism 8 is dipped into the chemical liquid 2 stored in the treatment vessel 1 together with the cassette 10. At this time, the photoresist and the like adhered to the surface of the wafer 9 is brought to come in contact with the chemical liquid 2 consisting of sulfuric acid and the like and the very fine bubbles of the gas 6 such as ozone and the like which are uniformly formed in the chemical liquid 2, the photoresist and the like are decomposed and removed from the surface of the wafer 9. As a result, the material to be processed can be treated quickly and effectively.