Machine-to-Machine (M2M) communication system is widely used and the number of M2M device is increasing day by day. When many M2M devices start transmitting simultaneously, frequent congestion and packet loss degrade a quality-of-experience (QoE).We propose transmit timing control method based on a QoE function index for reducing the congestion, and show the evaluation results to confirm an effectiveness of the method by an experiment using the 2.4GHz band ZigBee modules.