To provide a waste gasifying device capable of enhancing gasification efficiency of sludge.

In this waste gasifying device 1 equipped with a sludge supply means to supply sludge to the inside of a longitudinal gasifying furnace 3 having a charging port 9 through which waste is charged on the upper part of the furnace, a gas supply port 13 for supplying an oxidizer to the waste in the gasifying furnace 3 and the layer filled with sludge from the lower part, a gas exhausting port 11 to exhaust generated gas from the upper part of the gasifying furnace 3, and an exhausting means 15 to exhaust combustion residues produced by burning the waste and sludge from the bottom part of the furnace, a sludge charging means has a sludge supply pipe 31 inserted through the side wall of the gasifying furnace 3, and a cylindrical nozzle 35 provided by inclining it horizontally or downward in the gasifying furnace 3 by making it communicate with the tip part of the sludge supply pipe 31, the nozzle 35 is rotatably supported by the sludge supply pipe 31, and a plurality of sludge discharging holes are provided in the extending direction of the nozzle 35.