Polyethylene terephthalate scrap is depolymerized to bis-hydroxyethyl terephthalate and/or its oligomer (BHT) by supplying the scrap, together with ethylene glycol, to a reactor containing molten BHT under the following conditions(a) the molten BHT has a glycol to acid component equivalent ratio of 1.3 to 2.0(b) the ratio by weight of the acid component of the molten BHT to that of the polyester scrap is 1/4 to 2/1(c) the ratio of polyester scrap to ethylene glycol is such as to have a glycol to acid component equivalent ratio between the limits of 1.3 to 2.0.The depolymerization is performed at 215.degree. to 250.degree. C. with agitation of the reactants, after which a part of the product in the reactor be removed to a polymerizing reactor.