POTENTIAL MEASURING INSTRUMENT

PROBLEM TO BE SOLVED: To provide a non-contact type potential measuring instrument capable of improving measurement sensitivity.SOLUTION: A potential measuring instrument includes: a first shutter having multiple opening slits: and a second shutter having main slits whose number is the same as that of the opening slits and at least one of sub-slits. The first shutter and the second shutter generates states by a relative and reciprocative movement between both of the shutters: an open state to allow an electric field to pass between an electrostatic charged object and a detection electrode by allowing the positions of the opening slits to be coincident with the positions of the main slits or the sub-slits; and a closed state to perform blocking between the electrostatic charged object and the detection electrode by allowing the positions of the opening slits to deviate from the positions of the main slits or the sub-slits. The open state includes: a first open state where only the main slots face the opening slots; and a second open state where at least one of the opening slots faces the sub-slots.