This paper proposes a method of TCP multi-pathization for IoT network by SDN. The method distributes packets according to the congestion between paths and IP packet length. Since it is performed over SDN, no changes of existing protocols and devices are required. The authors implement the method by actual IoT devices and evaluate QoS by experiment. The results of the experiment show that the TCP throughput of the proposed method is higher than that of normal TCP when the difference in delay between multi-paths is low; but they also indicate that the TCP throughput of the proposal goes lower than that of normal TCP. To solve the problem, the authors proposes two modified methods. One is to switch the forwarding scheme according to the difference in delay between the paths. The other is to give delay to the path which has small delay. The paper shows the effectiveness of the modified proposed method by supplementary experiments.