PURPOSE: To recover a terephthalic anhydride capable of recycling in good efficiency, e.g., good heat efficiency and recovery percentage from waste PET bottle, etc., by heating waste polyethylene terephthalate, adding heated steam thereto, hydrolyzing the compound and separating the hydrolyzed material.

CONSTITUTION: (A) Waste polyethylene terephthalate is heated and (B) heated steam (e.g. heated steam containing sodium acetate) is added thereto and the material is hydrolyzed to separate and recover the hydrolyzed material. Specifically, e.g. the crushed material A and as necessary, further crushed polystyrene are charged into a container and the container is heated and water (containing sodium acetate) is heated by utilizing heat generated at this time to produce the steam B and the material A is hydrolyzed by charging the steam B into the container to separate and recover the hydrolyzed material.