A small-sized motor includes a field magnet attached to an inner circumferential surface of a metallic motor casing and having four or more magnetic poles. The field magnet is formed of a single ring-shaped magnet member having a predetermined thickness with respect to the radial direction and a predetermined length with respect to the thrust direction. At each of portions between the magnetic poles formed through magnetization, the magnet member has a thin portion having a reduced thickness with respect to the radial direction, the thin portion being formed by cutting the magnet member from the radially outward side. The magnetization is performed in the radial direction so as to alternately form S poles and N poles in the circumferential direction. At each of portions between the magnetic poles, the magnet member may have cut portions formed at opposite end portions of the magnet member with respect to the thrust direction.