To provide an automobile management system which can prevent the wrong use of cards, can repetitively use the same card and also can clear off the road devices used in a parking system.

The prepaid parking fare data and registered data are written into a readable/writable card 11, and an in-vehicle device 20 rewrites the fare data (remainder of fare). At the same time, the data on the card 11 are sent by radio to a portable out-vehicle device 30 from the device 20 and can be displayed at the device 30. Furthermore, the registered data can be sent by radio to a management center device 40 for the collation from the device 30.