To continuously supply a required amount of an oxidizing agent for supercritical water oxidation reaction without using air or gaseous oxygen as an oxidizing agent for the oxidation reaction.

This supercritical water reaction plant is provided with a supercritical water reactor 1 for subjecting organic matter to oxidation reaction with oxygen and also, this supercritical water reactor 1 is provided with an organic matter supply means 2, a water supply means 3 and a metal oxide supply means 4 and further, the supercritical water reaction plant is combined with a waste heat recovery equipment 7 that is a utility equipment. Organic matter used as a fuel is reacted with a metal oxide supplied as an oxidizing agent in the presence of supercritical water in the supercritical water reactor 1, generate heat.