PURPOSE: In a spreader stoker having a reversely-travelling-grate stoker for a coal fired boiler, to cause a stable combustion, by providing an auxiliary fire grate for ignition at the innermost part of a reversely-travelling-grate stoker.

CONSTITUTION: Auxiliary fire grates for ignition 3 consisting of inclined type fixed step grates is disposed at the innermost part A of a reversely-travelling- grate stoker 1, being secured to a rear water tube 9 with a hook 10. And in the lower rear of the auxiliary fire grates 3 is provided an air box 11, air preheated in an air heater of the boiler being supplied thereinto by a booster fan 13. In the arrangement state above, live coals are always formed on the auxiliary fire grates 3, coals spreaded thereon will instantly be ignited and burn by the radiant heat B from a combustion chamber 4 and drop on the stoker 1 as the stoker 1 advances, a layer of live coals thus being formed there on. In such a manner combustion is smoothly carried out all over the stoker 1.