To achieve high treatment capacity while controlling condensation of water vapor in desorption.

In this treatment method of the volatile organic compound by adsorbing the volatile organic compound included in a treated gas to be adsorbed to an adsorbent, desorbing the volatile organic compound adsorbed by the adsorbent, from the adsorbent by using the water vapor to mix the volatile organic compound in the water vapor in a pressurized state, and burning the water vapor in which the volatile organic compound is mixed, by a combustor, a container 11 for performing adsorption and desorption is divided into an inner chamber A and an outer chamber B by separating members 12, 13, 14 at least partially composed of the adsorbent, the container for performing the adsorption and desorption is kept warm, the treated gas is supplied to the inner chamber A and released to the outer chamber B through the separating members 12, 13, 14 in adsorption, and the water vapor is supplied to the outer chamber B and released to the inner chamber A through the separating members 12, 13, 14 in desorption.