A mass spectrometer provided with: a front mass separation section in which an ion having a predetermined mass-to-charge ratio is selected as a precursor ion among ions originating from a compound contained in a sample; a fragmentation section in which the precursor ion selected in the front mass separation section is fragmented into product ions; and a rear mass separation section in which the product ions generated in the fragmentation section are subjected to mass separation, and capable of performing an MSn analysis, wherein n is an integer equal to or greater than two, the mass spectrometer further comprising: a) a storage section storing a plurality of MRM measurement conditions and a plurality of data sets of standard multi-MRM spectrums respectively corresponding to a plurality of compounds, wherein each of the plurality of MRM measurement conditions include a plurality of MRM transitions, each of the plurality of MRM transitions being a combination of the precursor ion and the product ions, and each of the plurality of data sets of standard multi-MRM spectrums represents a mass spectrum indicating an intensity of product ions as a mass peak on a graph having mass-to-charge ratios of the product ions on one axis, the intensity of the product ions being measured by executing the MRM measurement condition, wherein the plurality of MRM transitions include three or more MRM transitions, each having a different mass-to-charge ratio of at least one of the precursor ion and the product ions; b) a target compound input receiving section for receiving an input indicating one or more target compounds by an operator; c) a measurement execution section for reading, from the storage section, the MRM measurement conditions respectively corresponding to the one or more target compounds, and measuring the sample under the MRM measurement conditions; d) a measured multi-MRM spectrum creation section for creating a measured multi-MRM spectrum indicating an intensity of product ions as a mass peak on a graph having mass-to-charge ratios of the product ions on one axis, the intensity of the product ions being acquired by measuring the sample; and e) a similarity degree calculation section for obtaining for each of the one or more target compounds, a degree of similarity between the standard multi-MRM spectrum stored in the storage section and the measured multi-MRM spectrum. a) a storage section storing a plurality of MRM measurement conditions and a plurality of data sets of standard multi-MRM spectrums respectively corresponding to a plurality of compounds, wherein each of the plurality of MRM measurement conditions include a plurality of MRM transitions, each of the plurality of MRM transitions being a combination of the precursor ion and the product ions, and each of the plurality of data sets of standard multi-MRM spectrums represents a mass spectrum indicating an intensity of product ions as a mass peak on a graph having mass-to-charge ratios of the product ions on one axis, the intensity of the product ions being measured by executing the MRM measurement condition, wherein the plurality of MRM transitions include three or more MRM transitions, each having a different mass-to-charge ratio of at least one of the precursor ion and the product ions; b) a target compound input receiving section for receiving an input indicating one or more target compounds by an operator; c) a measurement execution section for reading, from the storage section, the MRM measurement conditions respectively corresponding to the one or more target compounds, and measuring the sample under the MRM measurement conditions; d) a measured multi-MRM spectrum creation section for creating a measured multi-MRM spectrum indicating an intensity of product ions as a mass peak on a graph having mass-to-charge ratios of the product ions on one axis, the intensity of the product ions being acquired by measuring the sample; and e) a similarity degree calculation section for obtaining for each of the one or more target compounds, a degree of similarity between the standard multi-MRM spectrum stored in the storage section and the measured multi-MRM spectrum.