To save labor of fare adjusting work performed among a service management body, a trader indirectly related to the service management body, and a consumer receiving a service when a parking lot provider offers the service on a chargeable basis for the consumer purchasing a commodity from a retailer entrusting supply of the parking lot to the parking lot provider.

This fare adjustment method is provided with a charged amount data writing procedure for writing charged amount data about a charged amount for a predetermined service on a storage medium storing parking data, a charged amount data reading procedure for reading the charged amount data, a computing procedure for computing a fare adjustment amount on the basis of the charged amount data and the parking data, a fare adjustment amount displaying procedure for displaying the fare adjustment amount, and a fare adjustment procedure for adjusting the fare based on the displayed fare adjustment amount and an operation input for fare adjustment.