PROBLEM TO BE SOLVED : To provide a reservation system and electronic authentication system using the Internet and portable information terminals, capable of building a new lease and timeshare parking business by creating a new parking lot market not found among those existing markets.SOLUTION : Vacancy information for a parking lot owned by a real estate company is disclosed to a general user over the Internet or through a portable information terminal communication network. The user freely acquires the vacancy information on an hourly basis, daily basis, weekly basis or monthly basis, and reserves a parking lot. Moreover, the general user can receive an electronic authentication key for using the parking lot to be electronically authenticated at the parking lot in use, and electronically settle a usage fee. Further, the parking lot user already under monthly contract can sublease the parking lot on an hourly basis by disclosing the vacancy information to the general user, as far as the daytime in the vacant state is concerned.COPYRIGHT : (C)2007, JPO&INPIT