To perform maintenance service of the secondary battery of an electric motor car by a service server, which is set up on a communication network, causing it to correspond to the motor car provided with a communication network connecting function, and is accessed by the motor car.

The electric motor car 80 transmits battery control information and identification information to a service server. The service server 1 refers to battery control information received specifying the kind of motor car 80 from the identification information to power supply information DB22, and determines the quality of the battery. When there is no abnormality, a reply to that effect is transmitted, and when there is an abnormality, information for dealing with the abnormality is transmitted by E-mail.