Abstract: An apparatus as a suitable embodiment, wherein a reactor (102) has a nozzle (means for supplying a raw material, an oxidizing agent and water) (103), a high temperature and high pressure gas formed by reacting the raw material with oxygen or the like in an oxidizing agent under a water-containing atmosphere is introduced to a heat exchanger (104) which is provided between a pressure vessel (101) and the reactor (102), the pressure vessel (101) has a water inlet (114) connected with a water supply line (106) and an opening (117) for a discharge line (105) for a formed gas which is connected with the heat exchanger (104), and the nozzle (103) has a flow route for supplying water present between the pressure vessel (101) and the reactor (102) to the inside of the reactor(102); and a method for pyrolysis and gasification using the apparatus.