A portable mass spectrometer that is carried to a sampling site to conduct analysis incorporates measures against erroneous operation. To prevent erroneous operation, when a measurement sample cannot be accurately analyzed because of contamination in the measurement sample, a criterion for aborting the sample measurement is provided and mass spectrometer control maintenance is performed. When urine is measured, the mass spectrometer detects the substances contained in the urine and automatically determines whether the sample is urine. The mass spectrometer then automatically selects an analysis condition specific to urine samples to make a measurement. Also with respect to sweat and saliva, the mass spectrometer similarly selects a specific analysis condition. The mass spectrometer automatically determines whether a sample, which is an internal standard sample contained in a sample case, is being measured on a measurement-by-measurement basis and automatically displays any error, interrupts the measurement, or carries out other processing.