A portable quadrupole ion trap mass spectrometer includes an electron emission source, an ion trap including a ring electrode and first and second end cap electrodes arranged opposite sides of the ring electrode, and an ion detector for detecting an amount of ions discharged from the ion trap. The first end cap electrode includes a first aperture through which the electrons emitted by the electron source enter the ion trap, and the second end cap electrode includes a second aperture through which ions are discharged the ion trap. A first electron multiplier is disposed in the first aperture of the first end cap electrode and multiplies an amount of the electrons and input to the ion trap. An ion detector detects an amount of the ions discharged from the ion trap.