The invention provides a tire condition information collection apparatus and a relay apparatus thereof, which corrects a predetermined physical quantity within tire by use of a predetermined physical quantity outside tire in a vicinity of tire to inform of the corrected physical quantity. An air pressure and temperature of tire are detected by a detection apparatus 10 provided in each wheel 2. The detection data is transmitted from the detection apparatus 10 to a relay apparatus 20 disposed in the vicinity of each wheel by electromagnetic wave of a first frequency. When receiving the transmitted data, the relay apparatus 20 detects an atmospheric pressure and temperature in the vicinity of the wheel 2, and transmits the data to a main apparatus 30 along with the detection data received from the detection apparatus 10. The main apparatus 30 corrects the detection data of the detection apparatus 10 by use of the detection data of the relay apparatus 20, and displays the information obtained by applying the correction on a display panel to inform the driver of the information.