PROBLEM TO BE SOLVED : To provide an information processor that automatically collects empty house information and supports rental and/or sales on the basis of the empty house information collected.SOLUTION : The information processor comprises a main computer device connected to terminals via the Internet, and a phone number investigation system connected to an NTT switching system via a phone line. The main computer device includes resident information data for updating new resident information with latitude and longitude as necessary, map information data, and cumulative occupied/empty house information data, and has a built-in program for detecting these pieces of information and a built-in program for searching for and displaying empty house information. The phone number investigation system has a phone number sending computer device and, based on phone number investigation signals, detects how phone numbers are being used. The terminals search for empty house information so that the necessary empty house information can be displayed in the form of maps and characters.