Abstract: A magnetogenerator comprises a plurality of permanent magnets arranged orderly on an inner periphery of a fly-wheel with magnetic poles thereof being alternative, a plurality of power generating coils including an ignition power generating coil and arranged within the fly-wheel in opposing relation to the plurality of permanent magnets, and a trigger pole of an angle position detector provided on the fly-wheel. The plurality of permanent magnets include a plurality of adjacently disposed first magnets each having a first peripheral length, a pair of adjacently disposed second magnets disposed adjacent the first magnets peripherally of the fly-wheel and having a second peripheral length longer than the first length by l.sub.1 and a pair of third magnets disposed adjacent the second magnets, respectively peripherally, and having a third length shorter than the first length by l.sub.