To obtain a combustion device, capable of effecting complete combustion of synthetic solid fuel, produced from classified recovery refuse and containing much amount of ash constituent, efficiently without leaking any combustion gas or unburnt gas.

In a synthetic solid fuel combustion device, burning synthetic solid fuel on a hearth 1b, the hearth 1b is constituted of a first hearth 1b1, positioned at the upstream side of supplying direction of the fuel, and a second hearth 1b2, positioned so as to be neighbored to the downstream side of the first hearth 1b1. A fuel supplying means for sending out the synthetic solid fuel into a direction from the first hearth 1b1 to the second hearth 1b2 is arranged on the side peripheral wall of the first hearth 1b1 side and, further, a first plate member 94A, reciprocated to send out ash constituent or fuel on the first hearth 1b1 to the second hearth 1b2, is provided while a dam 17 is provided above the first hearth 1b1 near the second hearth 1b2 so as not to bother the sliding of the first plate member 94A. Further, a multitude of air passing ports 97 are formed on at least the first plate member 94A so that combustion air, supplied from the hearth 1b1, can be passed into a combustion chamber.