To accumulate telephone number information containing history of a telephone number such as change information and the use situation of the telephone number and to easily supply an investigation result in short time by providing a telephone number calling computer device executing the use situation investigation of the telephone number being an investigation object in accordance with telephone number investigation request data.

A user 1 is connected to an internet server 3 through the communication line of internet 2 and the like. The server 3 is connected to a telephone number calling computer device 4 for investigation at any time and the telephone number calling computer device 4 is connected to the digital exchange 5 of NTT. The exchange 5 is connected to a general service telephone 6 through the telephone line of ISDN. Present history information and telephone number history information are stored in a hard disk 7 contained in a computer 8 in the server 3 at every telephone number. The server 3 receives telephone number investigation request data and the telephone number calling computer device 4 executes the use situation investigation of the telephone number being the investigation object in accordance with the data.