Disclosed are a transmission device, a reception device and a method for providing a simultaneous data transmission for a data session through a plurality of heterogeneous networks. The transmission device divides particular data to be transmitted into two or more partial data, transmits first partial data after inserting first tunneling information which induces the first partial data to pass through a first network of two or more networks into the first partial data, and transmits second partial data of the two or more partial data after inserting second tunneling information which induces the second partial data to pass through a second network of the two or more networks into the second partial data.