A tire condition monitoring system comprising transmitters each of which is attached to one of a plurality of wheel assemblies of a vehicle and a receiver mounted on the vehicle, wherein the vehicle includes rotation angle detecting sections (21, 22, 23, 24) that detect rotation angles of the respective wheel assemblies, each transmitter includes a power source of the transmitter, a condition detecting section (32, 33) configured to detect a condition of a tire, a data generating section configured to generate transmission data that contains tire condition data indicating the condition of the tire detected by the condition detecting section (32, 33), a transmitting section configured to modulate the transmission data, which is generated by the data generating section, and transmit the modulated data, characterized in that: said transmitter includes further a storage section storing a correspondence relationship in which values of a specific bit among bits of the transmission data that change as the wheel assembly rotates are respectively assigned to specific angles set for a rotation angle of the wheel assembly, the specific bit including a least significant bit of the tire condition data or a bit that is calculated using the least significant bit of the tire condition data, and a transmission control section capable of performing specific angle transmission in which the transmission control section transmits the transmission data from the transmitting section when detecting that the rotation angle of the wheel assembly is any of the specific angles, the transmission control section is configured to transmit the transmission data at the specific angles that correspond to the specific bit of the transmission data, the receiver includes a receiving section configured to be capable of receiving the transmission data from the transmitters, an identifying section that, upon reception of the transmission data transmitted at the specific angle, identifies one of the wheel assemblies to which the transmitter is attached based on a detection value obtained from the rotation angle detecting section (21, 22, 23, 24), and a reception storage section that stores the correspondence relationship, the receiving section receives the transmission data from the transmitter that transmits the transmission data at the specific angle corresponding to the correspondence relationship, and the identifying section is configured to acquire the specific angle at which the transmission data has been transmitted based on the correspondence relationship and the specific bit of the transmission data received by the receiving section, and identify one of the wheel assemblies to which the transmitter is attached based on the specific angle. a power source of the transmitter, a condition detecting section (32, 33) configured to detect a condition of a tire, a data generating section configured to generate transmission data that contains tire condition data indicating the condition of the tire detected by the condition detecting section (32, 33), a transmitting section configured to modulate the transmission data, which is generated by the data generating section, and transmit the modulated data, characterized in that: said transmitter includes further a storage section storing a correspondence relationship in which values of a specific bit among bits of the transmission data that change as the wheel assembly rotates are respectively assigned to specific angles set for a rotation angle of the wheel assembly, the specific bit including a least significant bit of the tire condition data or a bit that is calculated using the least significant bit of the tire condition data, and a transmission control section capable of performing specific angle transmission in which the transmission control section transmits the transmission data from the transmitting section when detecting that the rotation angle of the wheel assembly is any of the specific angles, the transmission control section is configured to transmit the transmission data at the specific angles that correspond to the specific bit of the transmission data, the receiver includes a receiving section configured to be capable of receiving the transmission data from the transmitters, an identifying section that, upon reception of the transmission data transmitted at the specific angle, identifies one of the wheel assemblies to which the transmitter is attached based on a detection value obtained from the rotation angle detecting section (21, 22, 23, 24), and a reception storage section that stores the correspondence relationship, the receiving section receives the transmission data from the transmitter that transmits the transmission data at the specific angle corresponding to the correspondence relationship, and the identifying section is configured to acquire the specific angle at which the transmission data has been transmitted based on the correspondence relationship and the specific bit of the transmission data received by the receiving section, and identify one of the wheel assemblies to which the transmitter is attached based on the specific angle.