A charge amount measuring device, comprising:
- a container configured to have an internal gas exhausted therefrom;
- a beam emission part configured to emit a charged beam into the container;
- a first electrode disposed in a position where the charged beam emitted from the beam emission part collides;
- a second electrode disposed between the beam emission part and the first electrode, the second electrode being configured to be set lower in potential than the first electrode;
- a first measurement part configured to measure a position where the charge beam collides against the first electrode;
- and
- a second measurement part configured to measure a charge amount of a measurement subject disposed between the first electrode and the second electrode, based on the measured position.