A communication log storage section stores a communication log of emails exchanged with an external device over an external network. An acquisition destination-selecting section reads out the communication log and identifies an other-end party with whom a target user has performed transmission and reception of emails not less than a predetermined number of times to select the other-end party as an information acquisition destination. An information location-generating section extracts key information related to a location of information at the information acquisition destination contained in the emails transmitted and received to and from the information acquisition destination, to generate information location information. The information location information is stored in an information location-accumulating section. An information acquisition device acquires the information based on the information location information accumulated in the information location-accumulating section.