The invention discloses a sludge dryer, wherein a main shaft penetrates through a whole box body in the length direction of the box body, and is driven to rotate by a motor at one end of the main shaft; a plurality of pieces of round discs are arranged on the main shaft, a plurality of angle iron are fixed at the peripheries of the discs, the length of the angle iron is slightly less than the length of the box body, and the angle iron is parallel to the main shaft and is distributed in a radial manner; sludge pushing angle blades and sludge stirring sweep blades are arranged and fixed on the angle iron at equal intervals. According to the sludge dryer, hot air is adopted for drying the sludge in the box body, high-temperature hot wind generated by an electric heating unit radiator can be adopted as the hot air, the equipment is simple and the investment is less; through arranging the rotary discs and the angle iron, and additionally arranging the sludge pushing angle blades and the sludge stirring sweep blades on the angle iron, the sludge is pushed by using the bevels of the angle blades while the sludge is stirred, the structure is simple and good in reliability, the maintenance is easy and a better drying effect is realized.