In a system of this invention, an inquiring computer supplies a host computer with inquiry information indicated open or closed to third parties. The host computer applies inquiry information indicated open to a wide range of inquiring and answering computers, but does not apply inquiry information indicated closed to third party inquiring computers. Inquiry information indicated closed is applied to a small range including only the inquiring computer having inputted the inquiry information and answering computers. When answer search information is transmitted from the inquiring computer to the host computer, answer information supplied from an answering computer may be received through communication lines. Thus, the answer information for the inquiry information may be obtained efficiently while taking the security protection for the inquiry information presenting party into account.