To provide a biomass conversion type gas generator of a new structure facilitating improvement in operational safety and stability, and enabling efficient collection of useful combustible gases, by supplying air uniformly dispersed in the furnace thereby stably conducting oxidation and thermal decomposition reaction of biomass.

This biomass conversion type gas generator is equipped with partition walls 58 partitioning the bottom part of the furnace for oxidizing and thermally decomposing deposited vegetable fuels 20 to a plurality of divided areas 64 in the planar view, and each of the divided areas 64 can be supplied with air from outside independently.