'The invention is concerned with an ignition signal generator for internal combustion engines, consisting of a rotor and stators, wherein the rotor is constituted by a cylindrical magnet magnetized in the axial direction, and two disc-like magnetic pole pieces consisting of N pole and S pole attached to both side surfaces of the cylindrical magnet, the stators are so disposed that the two magnetic pole pieces are sandwiched therebetween, one end of each of the stators being faced to the N pole of the magnetic pole pieces and the other end thereof being faced to the S pole, and a pulser coil is wound on the central portion. Each of the two disc-like magnetic pole pieces is provided with stepped portions consisting of a portion larger than the outer diameter of the cylindrical magnet and a portion smaller than the outer diameter of the cylindrical magnet, the stepped portions in the periphery of the two magnetic pole pieces being coupled by a curve that changes gradually.