Recently, Peltier device is considered as a suitable device to generate thermal sensation. In order to control the reproduction of the sensation accurately, it is important to know the amount of heat inflow, which is the heat exchanged between a thermal system and an external environment. For that purpose, the authors proposed a heat inflow observer, which is a disturbance observer-based estimation method of heat inflow. However, in the past research, the observer was evaluated only from a qualitative point of view. In this research, another thermal sensor is put on the thermal system as an external environment, and the validity of heat inflow observer is experimentally confirmed using the sensor. The experimental results show the superiority of the proposed observer in obtaining the amount of heat inflow.