The present invention is a rotor for a vehicle a.c. generator which increases the operational life of the a.c. generator. The rotor, in the present invention for a vehicular a.c. generator includes a bobbin having a rotor coil for generating a magnetic field wound thereon and including fixing portions for supporting lead wires of the rotor coil; a pair of rotor cores for sandwiching the rotor coil and the bobbin therebetween; slip rings having terminals to be connected to the lead wires; grooves formed in the rotor core for housing the lead wires, the lead wires extending between the fixing portions and the terminals; and a rear fan provided so as to cover the grooves. The fixing portion, the terminal and the groove for each of the lead wires are provided so as to be substantially aligned, and the groove has an inward portion near an inner periphery of the rotor formed in a greater width than an outward portion near an outer periphery of the rotor.