This paper describe the case study of developing and providing the ontology-based educational information search service to overcome the limitations of the existing keyword-based search service. We used the OWL-DL 1) to build the core ontology DB from the existing metadata DB represented by the LOM, 2) to build the domain ontology DB of middle school Mathematics contents DB, 3) to merge the core ontology DB and the domain ontology DB. And both the OWL-DL and the SWRL are used to support the educational information search service. The system for the above service was built using the OWL-based deduction engine and the merged ontology DB, that process and deduct user query with enhanced simple and intuitional interface. This service is being provided as the demonstrational service by the EDUNET -- the largest nationwide learning contents search system in Korea.