Screw cooling unit of single-screw extruder contains a hollow screw with a sequentially arranged shank, a screw-tapped section and a tip, and a pipe placed in the screw cavity from the shank side for supplying coolant to the screw cavity. The end surface of the tip on the side of the screw cavity is equipped with an axial protrusion of a streamlined shape, and its peripheral part is made in the form of an annular hole of a streamlined shape.