To provide a biomass combustion device capable of facilitating both heating power adjustment and temperature control, obtaining high combustion efficiency, enabling automation throughout combustion continuation and extinction as necessary and capable of inexpensively achieving a safe use in many aspects.

The biomass combustion device includes: a combustion furnace body having a plurality of combustion chambers; a kiln body having a hot water storage tank and an air intake port etc. and provided at the upper side of the combustion furnace body; a fuel kindling port provided in the lower part of the combustion furnace body; an air exhaust device communicating with the combustion furnace body to suck exhaust gas and discharge it to outside; a fuel supply means to the combustion chambers; a normal temperature air supply device for supplying air from outside the combustion furnace body to the combustion chambers; a heating air supply device for supplying heating air to the combustion chambers by suction operation by the air exhaust device; and a control means for the supply operation by the fuel supply means, a normal temperature air amount, a heating air amount and a hot water temperature in the hot water storage tank, etc.