To provide a fire grate cooling mechanism capable of cooling a fire grate surely in a stoker type incinerator, whose fire grate for incinerating charged waste while transferring the same is constituted of a plurality of fire grate fractions arranged in the widthwise direction of the furnace.

Bar type supporting bodies 3 are formed hollow to constitute a cooling fluid flow passage 5 for conducting cooling fluid for cooling fire grates 2. On the other hand, the fire grate fractions 2 can be formed so as to be hollow for communicating holes to communicate the hollow parts of fire grate fractions 2 with the hollow part of the bar type supporting bodies 3, and can be formed to arrange a plurality of fire grate fractions 2 in the widthwise direction of the furnace to form cooling fluid flow passages 5 in respective fire grate fractions 2. In this case, respective cooling fluid flow passages 5 are communicated with each other, and a flow passage inlet port 5a introducing the cooling fluid into the cooling fluid flow passages 5 can be provided at the widthwise end of the fire grate pieces 2. Water is more preferable as the cooling fluid.