Rendering thermal sensation is useful for a machine that comes in contact with a human. For example, nursing robots can give a sense of security for patients, and communication robots can give a presence information for people who is in a remote location by using the technique of rendering. The methods about thermal sensation have been studied for many years. These studies usually use a thermoelectric conversion element called as a Peltier device that can both heat and cool by applying currents. Most of the conventional methods are not considered interference of heat flow between heat sources. In the case of applying these control methods for human interface, some heat sources have to be spread on the surface. Therefore, the influence of thermal interference has to be considered. In this paper, the method to estimate heat inflow eliminating the influence of thermal interference between multiple heat sources based on a heat inflow observer (HIOB) is proposed. The thermal system is modeled by a thermal network method including thermal interference between two Peltier devices. Some experiments are conducted to verify the proposed method.