A signal forwarding system includes: a plurality of signal forwarding devices forming a plurality of communication routes between a slave station and a master station; and a route control device that determines a communication route, wherein the route control device includes at least: a communication route calculation unit that calculates a communication route in response to a route switching request; and a forward destination setting instruction unit that outputs forward destination setting information based on the communication route, the signal forwarding devices include at least: a forward destination setting instruction acquisition unit that acquires the forward destination setting information; a forward destination set unit that changes a forward destination based on the forward destination setting information; and a forward unit that outputs input traffic based on the forward destination, and any of the route control device and the signal forwarding devices includes: a traffic monitor unit; a non-signal period estimation unit that estimates a non-signal period in which the traffic does not flow; and a switching timing control unit that controls a switching timing to perform route switching in the non-signal period.