To develop a system for checking indication and contraindication of medicines in prescription order entry system, a master table consisting of the disease names corresponding to the medicines adopted in a hospital is needed. The creation of this table requires a considerable manpower. We developed a Web-based system for constructing a medicine/disease thesaurus and a knowledge base. By authority management of users, this system enables many specialists to create the thesaurus collaboratively without confusion. It supports the creation of a knowledge base using concept names by referring to the thesaurus, which is automatically converted to the check master table. When a disease name or medicine name was added to the thesaurus, the check table was automatically updated. We constructed a thesaurus and a knowledge base in the field of circulatory system disease. The knowledge base linked with the thesaurus proved to be efficient for making the check master table for indication/contraindication of medicines.