Abstract: The present invention relates to waste treatment apparatus and method for combusting and treating wastes such as municipal wastes, refuse-derived fuel (RDF), and plastic wastes. The waste treatment apparatus (101) comprises a gasification furnace (5) for gasifying wastes (a) to produced combustible gas (m), a slagging combustion furnace (8) for combusting the combustible gas and melting solid components contained in the combustible gas to generate exhaust gas (j), a first filter (13a) for filtrating the exhaust gas discharged from the slagging combustion furnace and collecting fly ash (h1) contained in the exhaust gas, an injection device for injecting a neutralizer into the exhaust gas discharged from the first filter, a second filter for filtrating the exhaust gas, and collecting neutralized ash, a recovery device (14) for recovering the neutralized ash, and a conveying device (41a) for conveying fly ash collected by the first filter to the slagging combustion furnace.