A charge amount measurement method comprises: interposing a measurement subject between a first substance and a second substance having a through hole; measuring a first collision position where a charged beam passed through the through hole and vicinity of the measurement subject collides against the first substance, in a state that there is no potential difference between the first substance and the second substance, measuring a second collision position where a charged beam passed through the through hole and vicinity of the measurement subject collides against the first substance, in a state that there is a potential difference between the first substance and the second substance, and measuring a charge amount of the measurement subject based on a difference between the measured first collision position and the measured second collision position.