Abstract: A novel spinneret for producing superfine fibers having a total denier of not less than 20 denier and a monofilament denier of not more than 1.1 denier when winding up upon spinning is disclosed. The spinneret has nozzle orifices arranged in a lattice pattern extending toward a quench direction and the right angled direction to the quench direction. The arrangement is provided so as to satisfy the following formulas (1) to (4):(1/5)D.ltoreq.P.sub.i (P-1).ltoreq.(1/2)D (1)(1/2)D.ltoreq.Q.sub.i (Q-1).ltoreq.D (2)Q.sub.i /P.sub.i .ltoreq.2 (3)Q(P-1).ltoreq.H.ltoreq.P.times.Q (4)wherein D is an effective diameter of the spinneret (mm), P.sub.i is a nozzle orifice pitch in the quench direction (mm), P is the maximum number of nozzle orifices arranged in the quench direction, Q.sub.i is a nozzle orifice pitch in the right angled direction to the quench direction (mm), Q is the maximum number of nozzle orifices arranged in the right angled direction to the quench direction and H is a total number of the orifices.