A sensor device includes a detection electrode opposing an external electrode, and generating a voltage corresponding to a change in capacitance; a capacitive amplifier circuit having a first capacitor and a second capacitor, and configured to detect the voltage generated in the detection electrode, and output a detection signal obtained by amplifying the voltage generated in the detection electrode based on a capacitance ratio between the first capacitor and the second capacitor; a reset switch configured to reset the voltage of the detection electrode to a reference potential; a changeover switch configured to switch the capacitive amplifier circuit between a capacitive amplifier and a voltage follower; a second changeover switch configured to disconnect the first capacitor from the capacitive amplifier circuit; and a second reset switch configured to reset a voltage of the first capacitor to the reference potential.