The plastic mold decapsuling apparatus comprises an etchant bottle; a heat tank; an etchant reservoir disposed in the heat tank; at least one decapsuling plastic mold holder; a first etchant feeding pump for selectively circulating the etchant from the etchant bottle to the etchant reservoir and discharging waste etchant; and a second etchant feeding pump for feeding the etchant from the reservoir to the plastic mold holder. Since the etchant bottle can be set as it is without transferring the etchant into another vessel, the etchant handling work is safe. Since a required amount of etchant can previously be heated in a reservoir within the heat tank, it is possible to continuously supply a predetermined amount of etchant heated to a constant temperature, thus improving the speed of decapsuling work. Futher, since the etchant is circulated through the decapsuling plastic mold holder, it is possible to firmly decapsule plastic mold devices by use of a relatively mild etchant such as fuming nitric acid.