A device for inspecting the pressure, temperature, etc. in a tire includes a pressure sensor attached to a valve mounted on the tire rim and having an output that varies depending upon the tire internal pressure, and a resonator including a resonant coil and capacitor which resonates in the presence of an external radiation electromagnetic wave. An oscillation coil of an oscillator which generates the external radiation electromagnetic wave projects from the main body of the inspection device. The main body encloses a signal processor which detects and processes any change in oscillation state which has taken place at the oscillator, as caused by the resonance state of the resonator, and a display to display the result of the signal processing by the signal processor.