To estimate, from the level of proficiency in a relevant knowledge item, the level of proficiency in a knowledge item wherein an answer to a problem is not obtained.

Out of a skill map wherein a plurality of knowledge items required for acquiring proficiency in a certain field are set as nodes and made into a directed graph, the level of proficiency in the knowledge item of a link source whose link destination is a designated item is detected, and the degree of contribution set to the link between the designated item and the knowledge item of the link source is extracted. When the level of proficiency in the knowledge item of the link source is detected, the level of proficiency in the designated item is calculated on the basis of the detected level of proficiency and the extracted degree of contribution.