A CV conversion amplifier is provided that can secure a sufficient capacitance-to-voltage conversion gain and a sufficient amplitude range of an output voltage with a small consumption current. A capacitive sensor using the CV conversion amplifier is provided with low electric power, low noise, and a wide tolerance of input signals. The CV conversion amplifier accepts outputs, as inputs, from a first capacitance and a second capacitance whose capacitance is changed depending on a physical quantity and converts a capacitance value into a voltage.