A monitoring apparatus of a carrier is disclosed that includes a managing part that assigns a related carrier path ID to network configuration information and manages the related carrier path ID, the related carrier path ID uniquely defining a path span between the carrier and a related carrier; a receiving part that receives alarm information from a communications apparatus in the carrier, a selecting part that selects main cause alarm information from the alarm information; a determining part that determines whether the main cause alarm information affects the related carrier by determining whether the related carrier path ID is assigned to corresponding network configuration information in the main cause alarm information; and a transmitting part that transmits the main cause alarm information including the related carrier path ID and a generation location to the related carrier where the main cause alarm information is determined to affect the related carrier.