Mass spectrometer

A mass spectrometer, comprising:

• an ionization unit configured to ionize an analyte gas;
• a filter unit configured to allow passage of only a target ion which is a component of the analyte gas ionized in the ionization unit and which has a specific mass-to-charge ratio;
• and
• an ion detection unit configured to detect an ion detection value based on the target ion having passed through the filter unit,
• wherein the ion detection unit comprises
• a Faraday electrode which comprises an electrode portion disposed along a centerline of the filter unit and a bottom electrode provided at a position downstream of the electrode portion in a flow of the target ion so as to intersect with the centerline, the electrode portion and the bottom electrode being connected to each other,
• a secondary electron multiplier provided to face the electrode portion with the centerline located therebetween, and
• a blocking portion connected to the bottom electrode and configured to block a photoelectron and reflected light traveling toward the secondary electron multiplier.