To provide a combustion device of a small and transverse type for actualizing efficient combustion while preventing the scattering of dioxin and unburnt materials.

A cylindrical combustion device body 1 is installed in a transverse fashion. An ignition burner 7 is mounted at one end thereof, and a hot air jet port 4 is formed at the other end. A cylinder body 8 is provided at a bottom portion on the ignition port side, and a ceramic ball layer 13 and a primary air injection port 9 are provided on the inside thereof to form part of a primary combustion chamber 14. A burnt material supply port 19 is provided toward the ceramic ball layer 13, and a secondary air injection port 25 is provided between the primary combustion chamber 14 and the hot air jet port 4, where a secondary combustion chamber 26 is formed. A cover 28 encircling the combustion furnace body 1 is mounted thereon to form a blowing passage 29 therebetween, and a blower 30 is mounted on the inlet side. Air supplied into the blowing passage is put in contact with the outer face of the combustion furnace body 1 to be heated, and resulting hot air 34 is supplied from the primary injection port 8 and the secondary injection port 25.