A frame transmission device having a port for transmitting and receiving a frame and a learning table for storing a transmission source address included in the frame received at the port and the receiving port in association with each other includes: a port detector for detecting whether learning data coincident with the transmission source address included in the frame received at the port is stored in the learning table; a port judging unit for comparing a port learned in the learning data detected by the port detector to the receiving port; and a loop judging unit for judging on the basis of a time lapse from the storage of the learning data whether the frame is in a loop or not when the port learned in the learning data is not coincident with the receiving port.