A tire-mounted sensor is provided to check whether a chain is attached or not so that a monitor person manages a chain regulation based on a check result. Specifically, a communication center is notified of a vehicle in violation which is not in compliance with the chain regulation. Based on violation information which is communicated to the communication center, the monitor person easily identifies the vehicle which is in violation. In addition, whether the chain regulation is complied with or violated is stored in a memory circuit unit of the tire-mounted sensor as tire state data. When the monitor person sends an instruction command by using a tool, the tire state data is transmitted from the tire-mounted sensor to the tool. It is thus made possible for the monitor person to confirm whether the vehicle is in violation or not by simply referring to the tool.