Provided is a chromatography mass spectrometry capable of peak detection that can deal with a wide concentration range of a sample component and providing an evaluated value for the result. A plurality of samples having different known concentrations of a component are measured to detect a start point, an apex, and an end point of a peak. Regarding the start point, the apex, and the end point of the detected peak, an evaluated value such as probability is provided as a score to determine a score function. A component having an unknown concentration is measured to detect a start point, an apex, and an end point of a peak. Regarding the start point, the apex, and the end point of the detected peak, the score function is applied to evaluate peak detection results, and a result having a high evaluated value is selected as a peak.