There is provided a wireless sensor device capable of suppressing a reduction in detection sensitivity even if the distance between the wireless sensor device and a detection target is changed. A wireless sensor device 1 includes: a sensor unit 10 that generates a detection signal based on a transmission signal emitted to a detection target 30 and a reflection signal from the detection target of the transmission signal； and a signal processing unit 20 that performs signal processing on the detection signal generated by the sensor unit 10 . The sensor unit 10 generates a first detection signal Sa1 corresponding to a first phase state, which is a phase state of the transmission signal or the reflection signal, and a second detection signal Sa2 corresponding to a second phase state in which a phase of the transmission signal or the reflection signal is different from that in the first phase state. The signal processing unit 20 detects phase information based on the first detection signal Sa1 and second detection signal Sa2, and performs predetermined signal processing based on the detected phase information.
