To improve heat efficiency by reducing excessive air not to be used in secondary combustion.

In a pellet stove 10, the burning of flame F is reduced by increasing an amount (the number and sizes of primary air holes 49) of primary air, and by this, an amount (the number and sizes of secondary air holes 50) of secondary air is reduced, and the secondary air holes 50 are concentrated in a narrow range facing a lower part side of the flame F in a right side wall 12E. Consequently, since the secondary air is favorably supplied to the flame F and secondary combustion is promoted, the excessive air not used in the secondary combustion can be reduced even in either the minimum or the maximum combustion.