An asynchronous branching module (102) outputs transfer data received in accordance with a handshake protocol to any of branch destinations. An asynchronous arbitration module (101) merges transfer paths of the transfer data. A congestion detection module (111) receives an arbitration result signal from the asynchronous arbitration module (101) and outputs congestion information indicating presence/absence of congestion to a merge source. A congestion avoiding path calculation module (112) receives the congestion information and exclusively performs a process of storing the congestion information into a congestion information storage memory, and a process of making the asynchronous branching module (102) preferentially select, as a transfer branch destination, a branch destination generating no congestion information indicative of the presence of congestion from branch destinations leading to a destination, on the basis of the congestion information and the destination information of the transfer data.