The invention aims at making a volatile organic compound harmless, and in addition comprehensively improving the energy efficiency within a facility where treatment of the volatile organic compound is necessary. In the invention, in order to achieve this aim, a solution means is adopted where, a discharge gas containing a volatile organic compound is supplied to an adsorption apparatus to adsorb the volatile organic compound in an adsorbent. The volatile organic compound is desorbed from the adsorbent with pressurized steam and mixed with the steam. The steam containing the volatile organic compound is supplied, in the pressurized state, to the combustion chamber of a gas turbine, and burned together with a fuel gas.