A juice extractor comprising: a cover having an inlet port formed on one side of an upper part thereof and a rotary shaft hole formed in the center of an inner part thereof; a housing installed on a lower part of the cover, and having a guide jaw formed on a bottom of the housing, a draff outlet port and a juice outlet port formed apart from each other on a lower end part of the housing, a waterproof cylinder having a through hole and formed in the center of the lower end part of the housing, and a pressure discharge passage formed around a lower part of the waterproof cylinder; a screw having an upper rotary shaft formed on an upper part of the screw to be rotatably inserted into the rotary shaft hole, a plurality of screw spirals formed on an outer surface of the screw, an inner ring formed at a lower end of the screw to project downward and having a plurality of screw gears rotatably inserted into the pressure discharge passage, a lower space formed inside the inner ring to receive the waterproof cylinder therein, and a lower rotary shaft formed in the center of a lower part of the screw and a polygonal shaft hole formed thereon; a mesh drum insertable into the guide jaw of the housing, the mesh drum having a mesh structure formed on an outer wall of the mesh drum to discharge juice to the juice outlet port, and a plurality of wall blades longitudinally formed on an inner surface of the mesh drum; a rotary brush installed between the housing and the mesh drum to be rotated, and having a brush holder in which a brush for continuously sweeping the mesh drum and the housing is installed; and a drive unit having a polygonal shaft that is inserted into the polygonal shaft hole through the through hole of the waterproof cylinder, and rotating the screw at a low speed; wherein the housing accommodating the screw is longitudinally fixed to an upper side of the drive unit so as to press, grind and extract juice from materials put into the inlet port and to discharge the draff. a cover having an inlet port formed on one side of an upper part thereof and a rotary shaft hole formed in the center of an inner part thereof; a housing installed on a lower part of the cover, and having a guide jaw formed on a bottom of the housing, a draff outlet port and a juice outlet port formed apart from each other on a lower end part of the housing, a waterproof cylinder having a through hole and formed in the center of the lower end part of the housing, and a pressure discharge passage formed around a lower part of the waterproof cylinder; a screw having an upper rotary shaft formed on an upper part of the screw to be rotatably inserted into the rotary shaft hole, a plurality of screw spirals formed on an outer surface of the screw, an inner ring formed at a lower end of the screw to project downward and having a plurality of screw gears rotatably inserted into the pressure discharge passage, a lower space formed inside the inner ring to receive the waterproof cylinder therein, and a lower rotary shaft formed in the center of a lower part of the screw and a polygonal shaft hole formed thereon; a mesh drum insertable into the guide jaw of the housing, the mesh drum having a mesh structure formed on an outer wall of the mesh drum to discharge juice to the juice outlet port, and a plurality of wall blades longitudinally formed on an inner surface of the mesh drum; a rotary brush installed between the housing and the mesh drum to be rotated, and having a brush holder in which a brush for continuously sweeping the mesh drum and the housing is installed; and a drive unit having a polygonal shaft that is inserted into the polygonal shaft hole through the through hole of the waterproof cylinder, and rotating the screw at a low speed; wherein the housing accommodating the screw is longitudinally fixed to an upper side of the drive unit so as to press, grind and extract juice from materials put into the inlet port and to discharge the draff.