To easily lay out parts around a fan, and to increase air feeding efficiency.

A turbo-fan 71 for feeding combustion air to a burner 20 is located on the rear side of a casing bottom surface part 2b by inclining the injection direction forward from the vertical direction so that an exhaust port 71a is located just above the rotation shaft, that is, so that the part with a longer distance from the rotation shaft of the turbo-fan 71 to a casing is located at the uppermost part. As a result, the size of the depth W necessary for setting the turbo-fan 71 is reduced. As the blowing direction of the turbo-fan 71 is the same as the axial direction of a blast tube 72, the blast tube 72 can be formed straight to reduce the passage resistance.