A tire air pressure detecting device includes an air pressure detecting unit, a transmitting unit, a running state detecting unit, an air pressure change rate detecting section and a frequency adjustment section. The frequency adjustment section is configured to adjust a transmitting frequency at which the detected value of the tire air pressure detected by the air pressure detecting unit is externally transmitted by the transmitting unit according to the running state detected by the running state detecting unit and the air pressure change rate detected by the air pressure change rate detecting section. The frequency adjustment section is further configured to variably set a threshold value for switching the transmitting frequency from low frequency to high frequency according to the running state and the air pressure change rate.
展开▼