A rotor for a tandem type alternator and a tandem type alternator having such a rotor are disclosed. The rotor comprises front and rear Lundell-type rotor cores, carried on a rotary shaft adjacent to each other, which include front and rear rotor coils, respectively, and front and rear claw-shaped pole portions surrounding the front and rear rotor coils, respectively. The rear Lundell-type rotor core has a rear end face including a convexed portion, formed around the rotary shaft, in which a large diameter stepped portion of the rotary shaft and a plurality of relay terminals associated therewith are accommodated in an area close proximity to the rear Lundell-type rotor core, enabling an axial length of the rotary shaft between front and rear bearings to be shortened to increase the number of allowable maximum revolutions of the rotor by that extent.