A sensor apparatus includes an interface circuit to which one of a digital sensor and an analog sensor is connected as a sensor that generates an electric signal corresponding to a physical quantity of a detection target and a CPU that calculates the physical quantity of the detection target based on the electric signal generated by the sensor. The interface circuit has a first power supply circuit, a second power supply circuit, a receiver including a receiver circuit, and an operation determination circuit. The first power supply circuit generates an operating voltage of the sensor. The second power supply circuit generates a synchronizing signal for the digital signal. The receiver circuit receives an electric signal generated by the digital sensor. The operation determination circuit stops an operation at least of the second power supply circuit when the analog sensor is used.