To obtain a noncontact pressure sensor unit requiring no power supply.

The pressure sensor unit includes a sensor section 1 comprising a super magnetrostrictive material 10 generating a magnetic field corresponding to the pressure in a tire 101, a coil 12 generating an induction current corresponding to variation of a field generated in the super magnetrostrictive material 10, and a transmission coil 14 generating a field with the current induced in the coil 12, and a receiving section 2 disposed oppositely to the transmission coil 14 at the sensor section 1 and detecting the field generated in the transmission coil 14. A tire detector comprising the unit integrates the detection signal from the receiving section 2, compares the integrated value with a preset threshold value and delivers an alarm signal when the threshold value is exceeded.