Monitor system and identifier assignment method adopted in monitor system

In a device monitor system of the invention including multiple devices, a monitor apparatus, and a terminal that are mutually connected via a network, a serial number (first identifier of physically identifying the device) and a private address of the device are sent from the terminal to the monitor apparatus by e-mail. The monitor apparatus generates an installation ID (second identifier of logically identifying the device) correlated to the received serial number (first identifier), creates a document of a link for an HTTP request including the generated installation ID, a URL of the monitor apparatus, and the received private address of the device, and sends back the document to the terminal by e-mail. The user operates the terminal to click the link for the HTTP request and send the HTTP request to the device. The device receives and analyzes the HTTP request and stores the installation ID in a preset storage location. The device monitor system of the invention enables assignment of the second identifier of logically identifying the device to the device without requiring the user to go to the installation location of the device.