To suppress occurrence of dioxins or the like in a combustion exhaust gas when PCB is burned and decomposed by a burner.

A method for burning and decomposing a polybiphenyl chloride comprises the steps of mixing a reducing water having a lowered oxidation- reduction potential of -100 to -2,500 mV of 5 to 20% by volume with a liquid fuel containing the PCB and a liquid-like hydrocarbon, pressure-reducing, boiling, emulsifying the mixture, and then burning the mixture by a main burner 24 of a first combustion chamber 18. The method further comprises the steps of ejecting an air flow or a combustion flame from a first mixing burner 26 to the flame of the burner 24 to form a mixture flow, introducing the mixture flow to a second combustion chamber 20 via a throttle unit 16, ejecting a flame from a second mixing burner 28, and bringing about a mixture secondary combustion.