A brushless alternator of the present invention includes: a yoke whose inner circumferential surface is radially opposite via an air gap to a rotor revolvably supported by brackets; a stator supported by the brackets, for forming a magnetic circuit along with the rotor and the yoke; a bobbin for engaging with the outer circumferential surface of a thin portion of the yoke; a field coil wound around the bobbin, for producing magnetic flux; and a plate joined to the thin portion, for axially holding the bobbin; wherein the thin portion of the yoke and the other portion thereof are integrally formed in one piece using a single member.