A displacement detection device includes a piezoelectric sensor. The piezoelectric sensor is provided with a piezoelectric sheet on both principal surfaces of which detection electrodes are formed. When stress is applied to the piezoelectric sensor, charge is generated, and an output voltage in accordance with this generated charge is detected in a DC voltage detector. A controller measures this output voltage at a predetermined time interval. Every time the controller measures the output voltage, the controller makes a short-circuit control of a switch, and causes the charge generated in the piezoelectric sensor to be released. The controller can thereby detect an amount of change in output voltage generated at the predetermined time interval in accordance with an amount of displacement of the piezoelectric sensor. By sequentially integrating this, the controller can accurately detect the amount of displacement of the piezoelectric sensor which changes across measurement timings.