We have proposed a method for diagnosing analog circuits that is realized by combining the operation-region model and the X–Y zoning method. In the method, we could implement a diagnosis procedure based on a diagnostic method for digital circuits because we developed a data processing method to handle data discretely. In this paper, we improve the method by using an adaptive test to obtain a shorter diagnostic sequence length and show its characteristics. Moreover, we propose a new data processing method that utilizes the output response of a circuit to obtain better diagnostic performance. We demonstrate the effectiveness of the proposed methods by applying them to ITC'97 benchmark circuits with hard faults and soft faults. These improved methods can reduce the diagnostic sequence length without degrading the performance of diagnostic resolution and CPU time.