A traffic control method can prevent that the number of cells transmitted to an ATM network exceeds a maximum transmission rate. When a frame F is transmitted from a frame relay network FR1 to an IWF, a traffic control part included in the frame relay network FR1 measures the transmission data quantity for a measuring time in a DLCI connecting the frame relay network FR1 and the IWF. Successively, the traffic control part detects a traffic restrictive level corresponding to the measured transmission data quantity. Then, the traffic restrictive process corresponding to the restrictive level is performed, and the frame transmission is controlled by the transmitted terminal of the frame F. Thus, it is prevented that the number of cells transmitted to the ATM network exceeds a determined maximum transmission rate.