In fusion plasmas, plasma fluctuations grow because of the collective behavior of charged particles constituting the plasma (magnetohydrodynamic instability, MHD instability) and they can cause rapid degradation of the plasma confinement performance. In order to understand the characteristics of the MHD instability, magnetic field fluctuations outside the plasma and density and temperature fluctuations are measured and time series data analysis of these fluctuation signals is performed. In this topic, we will learn the fluctuation analysis method for MHD instabilities observed in LHD plasmas. Specifically, students will learn the most basic Fourier analysis and advanced analysis methods such as wavelet analysis, and implement the analysis tools by programming.