A control apparatus for an on-vehicle generator is provided. The generator, driven to rotate by an on-vehicle engine, is provided with stator windings, rectifiers, a field winding, and a voltage control apparatus (i.e., the control apparatus for the on-vehicle generator). The voltage control apparatus comprises a switching element (including power transistors, for example) selectably and electrically connects or disconnects a current path between the field winding and a power supply to provide the field winding with current; a storage element (for example, a battery); and a regeneration element (for example, free wheel diodes) provides the storage element with current flowing through the field winding when the switching element is turned off.