1. A method of searching for an instance path based on an ontology schema, the method being performed by an instance path search apparatus, the method comprising: (a) receiving two or more keywords from a user and generating a pair of instances with respect to the keywords, respectively; (b) extracting a pair of classes corresponding to each of the pairs of instances from an ontology instance database, respectively; (c) obtaining an ontology schema path with respect to each of the pairs of classes from an ontology schema path database, respectively; and (d) replacing start and end classes with corresponding first and second instances in each of the ontology schema paths and searching for an instance path connected between the first instance and the second instance, respectively.