There is provided a rotor of a rotating electrical machine including a pair of field core bodies that are provided so as to enclose the field coil via the insulation bobbin around which the field coil is wound, in which a claw-shaped magnetic pole extending from an outer circumferential section of the field core body in an axial direction is provided on the field core body. The insulation bobbin has a plurality of flange sections extending from the base section of the claw-shaped magnetic pole along an inner surface of the claw-shaped magnetic pole of the field core body, and a plurality of thin portions are formed in the root section of the flange section at intervals in a circumferential direction.