In the spectrometer, heavy loads are arranged centrally inside a case having a height smaller than a width, and having a depth smaller than the height. The heavy loads include a vacuum chamber, a vacuum pump which evacuates the vacuum chamber, a sample introduction unit which introduces a sample to be measured and evaporates the sample, an ionization unit which ionizes the evaporated sample and provides it to the vacuum chamber, and an ion detection unit which is connected to the vacuum chamber. Circuit board storage units which store a plurality of circuit boards with a predetermined space therebetween are formed on both sides along a width direction of the case.