To provide an inexpensive and compact carbonizing apparatus capable of corresponding to various kinds of raw materials, capable of providing a carbonized product with a stable quality, capable of suppressing the generation of dioxins, having high thermal efficiency and excellent in productivity.

This screw-conveyor carbonizing apparatus used by charging the raw material form a charging opening and continuously discharging the carbonized product from a discharging opening is obtained by forming double and nearly cylindrical outer heat pipes pivotally supporting screw conveyors continuously installed in the upper and low direction into one pair, forming the plural pairs nearly horizontally arranged in a casing having a nearly rectangular shape into one unit, and combining plural units in the upper and lower direction. If necessary, the diameters of the outer heating pipes at the lower position are reduced by the unit, and the raw material is carbonized by feeding hot air into the casing and heating the outer heat pipe.