The present invention prevents the degradation of the power generating efficiency of an alternating current generator by preventing the expansion of an air gap formed between pole cores and a stator core, achieves low-noise operation by preventing generation of high-frequency impact magnetic noise, and makes it possible to relieve strains applied on a magnet holder. The present invention utilizes sixteen magnets, each of which fits between two of sixteen claw-like magnetic poles formed on the outer periphery of Lundell-type pole cores, which rotates integrally with a shaft. The magnets are caught and stopped by a magnet holder which has been formed by interconnecting zig-zagging segments and has elasticity as a whole. Here, the permanent magnets are held by the magnet holder so that the magnet holder does not protrude towards the rotor side from the outer peripheral face of the Lundell-type pole cores and the contacting faces of the magnet holder contact the outer faces of the permanent magnets. The claw-like magnetic poles are disposed so as to face the stator.