A performance deterioration detecting apparatus configured to detect a performance deterioration start state of an energy storage device. The performance deterioration start state is an initial state of deterioration in performance of the energy storage device. The apparatus includes a performance deterioration determiner configured to determine that the energy storage device is in the performance deterioration start state based on a displacement of peak position in a capacity-voltage property of the energy storage device with time. The capacity-voltage property indicates a relation between a capacity variation amount (dQ/dV) and a voltage (V).