A companion device interoperating with a broadcast reception device for receiving a broadcast service, includes a communication device configured to connect the companion device with the broadcast reception device; and a controller configured to receive emergency alert information from the broadcast reception device, the emergency alert information including identifier information for the emergency alert information, category information of the emergency alert information, and priority information for the emergency alert information, wherein a value of the priority information represents one of 5 levels of priority of the emergency alert information, the 5 levels represents the priority from low priority to high priority, and in response to a change of the priority, the controller receives changed emergency alert information including changed priority information of which a value represents a level of the changed priority.