NOVELTY - The method involves measuring internal resistance of electrical storage apparatus (1), and computing initial stage state of health (SOH) of electrical storage apparatus from measured value of internal resistance. The internal impedance of electrical storage apparatus is measured by signal of preset frequency increasing with raise of temperature. The inside temperature of electrical storage apparatus is computed from impedance measured value of the internal impedance. The initial stage SOH is corrected and SOH is estimated using calculated value of inside temperature.    USE - State detection method of electrical storage apparatus such as lithium ion secondary battery and electrical double layer capacitor mounted in energy-saving motor vehicle, hybrid vehicle and electric vehicle. Uses include but are not limited to battery of motor vehicle, battery pack of mobile telephone and battery of personal computer.    ADVANTAGE - The deterioration state and charge condition of the electrical storage apparatus can be detected correctly. The exact temperature of the electrical storage apparatus can be grasped. The generation of error in determination of the deterioration state can be avoided. The correction of the initial stage SOH can be performed based on exact inside temperature. SOH of the electrical storage apparatus can be correctly detected. The influence on internal resistance by the difference in SOC can be reduced reliably. The resistance of the electronic conductivity of the electrical storage apparatus depending on temperature can be measured. The fall of the measurement precision of the internal impedance by the noise from the charging circuit can be prevented, and the calculation precision of temperature can be maintained highly. The influence of load can be made small in the measurement of the internal impedance.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view illustrating the state detection method of the electrical storage apparatus. (Drawing includes non-English language text)    Electrical storage apparatus (1)    Electric current detection unit (4)    Voltage detection unit (6)    Inside temperature calculation unit (7)    State calculation unit (8)