A wireless sensor apparatus includes first and second polarization antennas whose polarization surfaces of radiation waves are mutually orthogonal, a first mixer circuit connected to the first polarization antenna and configured to input a first reception signal received by the first polarization antenna, a second mixer circuit connected to the second polarization antenna and configured to input a second reception signal received by the second polarization antenna, a signal generation circuit configured to generate pulse signals fed to the first and second polarization antennas and also supplied to the first and second mixer circuits, and a differential amplification circuit configured to perform a differential amplification on a mixed output obtained by mixing the first reception signal and the pulse signal by the first mixer circuit and a mixed output obtained by mixing the second reception signal and the pulse signal by the second mixer circuit.