A transmission system that uses resources of a transmission network efficiently to a request of dynamic bandwidth guarantee from a communication network while controlling a load of a managing server, and connects a logical path of the communication network and a logical path of a transmission network. In the transmission system that has multiple transmission nodes each serving as a component of the transmission network, multiple communication nodes each serving as a component of the communication network, and a managing computer, when an available bandwidth of a default path is smaller than a guaranteed bandwidth contained in control information and then when information about the logical path already having been dynamically constructed coincides with a condition, a logical path that uses a route different from a specified default path is dynamically constructed as a logical path in the transmission network.