PURPOSE: To reduce the scale of equipment for the system by devising the system such that ATM cells are separated while switching the ATM cells during the routing of an STM-m signal to plural STM-n signals.

CONSTITUTION: A multiplexed STM-16 signal 101 is inputted to a routing control circuit 1 and gates 2-1 to 2-4. The signal 101 includes ATM cells, connection information representing the connection from the STM-16 to an STM-4 signal and connection destination information representing the connection from the STM-16 to an STM-1 signal. The circuit 1 discriminates which of gates 2-1 to 2-4 is to be through and gives control signals 102-105 to the gates 2-1 to 2-4. Output signals 106-108 in the multiplexed STM-16 are given to buffers 3-1 to 3-3 through the gates 2-1 to 2-3 according to the control signals 102-104 from the circuit 1, and the signals are converted and STM-4 output signals 109-111 are outputted. Similarly, buffers 6-1 to 6-4 output STM-1 outputs as signals 121-124.