A permanent-magnet generator is provided that has a bowl-shaped fly wheel integrally formed with a boss part by casting or hot forging, that reduces rotational imbalance and the quantity of balance correction processing such as drilling. The permanent-magnet generator has a bowl-shaped fly wheel produced by casting or hot forging, having a circumferential wall part and a bottom wall part, and having a boss part for supporting a rotating shaft, the boss part being integrally formed at the center of the bottom wall part. The plural vents are arranged substantially circularly in the bottom wall part of the fly wheel, and a key groove for coupling with the rotating shaft is provided at a part of the boss part. The arrangement of at least one of the plural vents is made unequal in order to reduce rotational imbalance including that caused by the key groove.
