In a requirements elicitation using ontology, the quality of elicited requirements fully depends on the quality of requirements ontology. In this paper, a verification method of the correctness of requirements ontology is proposed in order to improve the quality of requirements ontology. We provide a rule description language to specify properties that requirements ontology should satisfy. Then, by checking whether the rules are consistent with requirements ontology, we verify the correctness of the ontology. Both the verification method and a prototype system based on the method will be illustrated with examples.