A tire condition acquisition device located in a tire and that transmits at least tire internal air pressure information includes: a housing that allows outside air to enter in only through a ventilation hole; an air pressure detecting element disposed in the housing and that detects an air pressure of air that enters in through the ventilation hole, and converts the detected air pressure to an electric signal which is then output; and a transmission circuit disposed in the housing and that transmits the detected air pressure information via electromagnetic waves based on the electric signal output from the air pressure detecting element; wherein at least the ventilation hole and an area peripheral thereto are treated so as to be water repellent.