An ion detector includes a microchannel plate configured to generate secondary electrons upon reception of ions incident thereon and multiply and output the generated secondary electrons; a plurality of electron impact-type diodes configured to have effective regions narrower than an effective region of the microchannel plate, receive the incident secondary electrons output from the microchannel plate, and multiply and detect the incident secondary electrons; a focus electrode configured to be disposed between the microchannel plate and the electron impact-type diodes and focus the secondary electrons toward the electron impact-type diodes; and a voltage supply part configured to apply a drive voltage to each of the plurality of electron impact-type diodes.