In recent research, pattern recognition method has been widely used by many researchers for fault diagnoses of mechanical systems. Also it determines the soundness of a mechanical system by detecting variations in the systems's vibration characteristics. Hidden Markov model (HMM) has recently been used as pattern recognition methods in various fields. In this study, a HMM method for the fault diagnosis of a rotating machine with bearing fault is introduced. The existence, location, and quantity of bearing fault are identified. Also Fast Fourier Transform (FFT) is employed to extract feature vector.