A combustion device includes a device main body having a combustion chamber installed above a cyclone melting furnace configured to combust a pyrolysis gas generated from a waste material after incineration while turning the pyrolysis gas, and configured to combust an unburnt gas discharged from the cyclone melting furnace. Further, the combustion device includes a plurality of sidewall boiler water pipes configured to cover a sidewall of the device main body from a periphery thereof and extending along the sidewall throughout upward and downward directions of the device main body.