To provide a tire condition monitoring device capable of informing of the abnormal condition of a tire in responsive to the speed of a vehicle.

A controller 44 of a transmitting/receiving unit 40 determines the numbers for transmitting an address electric wave for a unit time (for example, one minute) based on an inputted vehicle speed signal. As a result, an interval of time for transmitting the address electric wave is determined. Namely, the number for transmitting the address electric wave for a unit time is increased at the high speed traveling of the vehicle as compared with the time of stopping of the vehicle and the low speed traveling. Namely, the number for transmitting the address electric wave for a unit time is increased as the speed of the vehicle becomes faster. Therefore, when the abnormal status of the tire is generated at the high speed traveling of the vehicle, the matter is quickly warned and displayed on an indicator 50. As a result, the abnormal state of the tire can be quickly informed to a driver at the high speed traveling of the vehicle.