In a chromatograph mass spectrometer capable of defining an appropriate measurement time range and selectively performing a scan measurement, selected ion monitoring (SIM) measurement or simultaneous scan/SIM measurement in that time range, a total ion chromatogram 51 obtained by a scan measurement of a standard sample and a previously-created compound table 52 are displayed on the screen of a display unit in the process of setting parameters in a measurement condition table. An operator selects a compound that should undergo the simultaneous scan/SIM measurement, then places a checkmark in an appropriate check box in the compound table 52, and finally clicks the “Auto-Create” button 54. Then, a measurement time range for the selected compound is defined by adding a time span before and after the retention time of that compound, respectively, and a measurement condition table 53 is automatically created and displayed on the screen. This table includes instructions for performing a simultaneous scan/SIM measurement at specific mass-to-charge ratios characteristic of the selected compound during the aforementioned measurement time range.