The condition monitoring system includes an acquisition unit and a generation unit. The acquisition unit acquires waveform data from a measuring device to measure an electrical signal that is either output or input of a converter. The waveform data represents a waveform of the electrical signal. The generation unit generates, based on the waveform data, analysis data to monitor the condition concerning the converter. The generation unit obtains, by frequency analysis, a plurality of combinations, each including a value of a frequency and a value of a feature quantity that is either intensity or phase, based on the waveform data when a value of the drive frequency varies and thereby generate the analysis data having at least three variables including the frequency, the feature quantity, and the drive frequency.