The conventional relay device has a problem that a traffic load on a communication device is large when an output port of a frame including a destination address, which an address table has not learned yet, is a port connected to a branch circuit, since flooding is performed on all ports except for a port that has received the frame. A relay device (21) is provided with a destination determination unit (41) to transfer, when a time clocked by a timer unit (40) to start clocking is within a set time, a frame to ports (511 and 512) connected to trunk circuits (61 and 64), and when the time clocked by the timer unit (40) exceeds the set time, to transfer the frame to the ports (511 and 512) connected to the trunk circuits (61 and 64) and a port (513) connected to a branch circuit (65), in a case wherein it is impossible for a search unit (43) to obtain from a first storage unit (33) a port number corresponding to a destination address included in the frame received, and the first storage unit (33) is cleared.