To provide a screw conveyor capable of efficiently breaking transported objects into fragments.

A screw conveyor is composed of: a transportation pipe; a screw 2 disposed in the transportation pipe; and driving means which rotates the screw 2. The screw 2 comprises: a screw shaft 5 serving as a rotation shaft; a screw blade 3 disposed along the screw shaft 5 in a spiral manner; and paddles 4 attached along the screw shaft 5 at a predetermined interval. A height of each paddle 4 is set so as to be equal to or lower than a height of the screw blade 3, and a side surface of the paddle 4 is obliquely disposed relative to the screw shaft 5 so as to form an acute angle therebetween.