To provide a management device for common use of parking lots which allows plural specific users to share the parking lots.

A 2nd server 102 is equipped with a member database 102A in which contracting members and member identification numbers are related and stored and a parking lot database 102B in which information regarding the use states of respective contracting parking lots is stored. According to data, inputted by the Internet by using a telephone communication line, on an area and a time zone in which a parking lot is to be used, a usable parking lot retrieving means retrieves usable parking lots from the parking lot database and sends a candidate list of vacant parking lots. According to a parking lot reservation sent from a contracting member, the reserved parking lot and reserved time zone are written to the parking lot database, the use result is written to the member database, and the sale result is written to a sale database; and a reservation number is sent to the mentioned contracting member.