A method and apparatus is used to confirm the charge amount and degradation state of a battery. Various cycle test battery measurements are conducted at prescribed time intervals until the end of the battery life, and the measured values are used to generate a determination table or determination tables showing relationships between battery charge amount and degradation state. To establish the charge amount and degradation state of a subject battery, the subject battery is measured and the results compared with determination table values. The existing charge amount and the state of battery degradation are estimated in accordance with a determination table location of matching values.