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 from an ontology instance database a pair of classes where each of the pairs of instances belongs, respectively; (c) finding an ontology schema path connected between two or more classes with respect to each of the pairs of classes from an ontology schema path database, respectively, wherein the ontology schema path refers to a route where two or more classes are connected to each other with one or more relationships; and (d) replacing start and end classes with corresponding first and second instances in each of the ontology schema paths connected between two or more classes and searching for an instance path connected between the first instance and the second instance, respectively, wherein the instance path refers to a path in which instances are connected via one or more relationships, wherein step (d) comprises: (d-1) replacing the start and end classes with corresponding first and second instances in the ontology schema path; (d-2) dividing the ontology schema path into halves and generating a first join schedule including the first instance and a second join schedule including the second instance; (d-3) if there is a class connected to the first instance or second instance based on the first or second join schedule, extracting at least one instance connected to the first instance or second instance from instances included in the connected class; and (d-4) generating instance paths in which the extracted instances are connected between the first instance and the second instance.