A method of continuous hydrothermal carbonization of sludge containing organic matter involves a step of hydrothermal reaction carried out in a reactor, and at least one cooling step in which the sludge having undergone the hydrothermal reaction step is cooled. The hydrothermal reaction step includes: a step of injection of sludge in which the sludge is injected into the reactor by a first inlet; a step of injection of steam in which steam is injected into the reactor by a second inlet, the second inlet being distinct from the first inlet; a step of circulation, in which a mixture consisting of the sludge and the steam injected into the reactor is placed in circulation within the reactor; a step of continuous extraction of at least a portion of the mixture contained in the reactor by a sludge outlet. Also disclosed is a device for carrying out such a method.