This study investigates a method to represent the knowledge of disease diagnosis procedure of doctors as a decision tree by the RDR (Ripple Down Rule) technique and to reconstruct it to an effective procedure by the ID3 (Iterative Dichotomiser 3) technique. In the reconstruction, the clinical system is considered as restrictions. The proposed method is implemented as an interface system by the Java. The applicability of the proposed method is examined by sample problems for disease diagnosis of hands.