A mass spectrometer including: an ionization chamber (11) that generates ions from a sample, a collision cell (222) located downstream from the ionization chamber (11), a mass separation unit (2412) located downstream from the collision cell (222), an energy barrier unit (223) located between the collision cell (222) and the mass separation unit (2412), a voltage application unit (30) that applies a voltage to each of the ionization chamber (11), the collision cell (222), and the energy barrier unit (223), and a control unit (42) that controls the voltage application unit (30) such that a potential of the ionization chamber (11) is set to a first potential, a potential of the collision cell (222) is set to a second potential that is lower than the first potential, and a potential of the energy barrier unit (223) is set to a third potential between the first potential and the second potential.