A mixing apparatus for crushing sludge comprising: a motor part having a rotary shaft inserted into the motor part and penetrating the motor part from a first side to a second side, a moving part formed to penetrate the motor part from a first side to a second side and move a chemical which is fed by an outside chemical feeder to the second side; a paddle mounted at the shaft on the second side of the motor part to be rotated based on the rotation of the shaft and/or of the motor part and to spray the chemical, wherein the motor part comprises: a main body in which the rotary shaft is inserted; a first plate combined with the first side of the main body and one outer circumference of the shaft; and a second plate combined with the second side of the main body and another outer circumference of the shaft, wherein the second plate comprises: a second bearing part combined with an outer circumference of the shaft; a second sealing part combined to surround the second bearing part around an outer circumference of the second bearing part; and a securing part surrounding the second bearing part and the second sealing part, and securing the second bearing part and the second sealing part at or to the second side of the motor part, characterized in that a plurality of saw-toothed parts is disposed at the outer circumference of the paddle in the length and outside direction to crush the sludge while the paddle is rotating and form a flock by mixing the chemical with the sludge. a motor part having a rotary shaft inserted into the motor part and penetrating the motor part from a first side to a second side, a moving part formed to penetrate the motor part from a first side to a second side and move a chemical which is fed by an outside chemical feeder to the second side; a paddle mounted at the shaft on the second side of the motor part to be rotated based on the rotation of the shaft and/or of the motor part and to spray the chemical, wherein the motor part comprises: a main body in which the rotary shaft is inserted; a first plate combined with the first side of the main body and one outer circumference of the shaft; and a second plate combined with the second side of the main body and another outer circumference of the shaft, wherein the second plate comprises: a second bearing part combined with an outer circumference of the shaft; a second sealing part combined to surround the second bearing part around an outer circumference of the second bearing part; and a securing part surrounding the second bearing part and the second sealing part, and securing the second bearing part and the second sealing part at or to the second side of the motor part, characterized in that a plurality of saw-toothed parts is disposed at the outer circumference of the paddle in the length and outside direction to crush the sludge while the paddle is rotating and form a flock by mixing the chemical with the sludge. a main body in which the rotary shaft is inserted; a first plate combined with the first side of the main body and one outer circumference of the shaft; and a second plate combined with the second side of the main body and another outer circumference of the shaft, wherein the second plate comprises: a second bearing part combined with an outer circumference of the shaft; a second sealing part combined to surround the second bearing part around an outer circumference of the second bearing part; and a securing part surrounding the second bearing part and the second sealing part, and securing the second bearing part and the second sealing part at or to the second side of the motor part, characterized in that a plurality of saw-toothed parts is disposed at the outer circumference of the paddle in the length and outside direction to crush the sludge while the paddle is rotating and form a flock by mixing the chemical with the sludge. a second bearing part combined with an outer circumference of the shaft; a second sealing part combined to surround the second bearing part around an outer circumference of the second bearing part; and a securing part surrounding the second bearing part and the second sealing part, and securing the second bearing part and the second sealing part at or to the second side of the motor part, characterized in that a plurality of saw-toothed parts is disposed at the outer circumference of the paddle in the length and outside direction to crush the sludge while the paddle is rotating and form a flock by mixing the chemical with the sludge.