Abstract: A method for assigning a peak code using a region partition scheme, the peak code for use in the method, and a method for diagnosing a faulty operation of the mechanical device using the peak code are disclosed. The method analyzes a frequency of either a unique operation sound or vibration signal generated when each normal-status mechanical device is operated, acquires a normal peak code, and compares the acquired normal peak code with a measurement peak code acquired by analyzing a frequency of either a unique operation sound or vibration signal measured from a measurement-objective mechanical device, such that it determines the presence or absence of a faulty operation of each mechanical device according to the result of the comparison.