As soon as a set of data is acquired by a mass spectrometric analysis, an accumulated value of the signal intensity on the mass spectrum is calculated for each m/z segment obtained by dividing the entire m/z range covered by the measurement by a predetermined m/z width. Only the m/z segments with accumulated signal-intensity values equal to or greater than a predetermined threshold are selected as the target for an MS/MS analysis. MS/MS analysis is performed for each selected m/z segment, using ions whose m/z values fall within the m/z segment as precursor ions. A measurement cycle which includes mass spectrometric analysis performed one time and MS/MS analysis performed one or more times is repeated. After that, ions originating from the same component are selected based on the retention time of a peak in an extracted ion chromatogram created for each product ion, and the component is identified.