An electric potential fixing apparatus is provided that can prevent the combined total amount of electricity of a connection line between the first capacitance and the second capacitance from changing even when the electric potential of the connection line between the first capacitance and the second capacitance is fixed in the case where the first capacitance and the second capacitance are directly connected.
This electric potential fixing apparatus has the first high resistance (3) and the second high resistance (4) and includes a voltage supply circuit (1) that preserves the combined total amount of electric charge of a measuring capacitance (14) and a fixed capacitance (15) and maintains constant the electric potential of a signal line (17) that connects the measuring capacitance (14) and the fixed capacitance (15). And an output terminal (5) of the voltage supply circuit (1) is connected to the signal line (17).