Technique of rendering thermal sensation can connect people who are in remote locations, such as teletherapy and a multimodal system. Humans feel detailed temperature distribution and recognize the characteristic of a contacting object. Although, conventional method can only render the thermal sensation of a fingertip or a part of a hand. In the case of combining these techniques with robot for human support, the robot can only touch one point of a material. This paper proposed the method of temperature control for rendering thermal sensation considering spatial diffusion. The method can spread the area of rendering and help rendering spatial sensations. The validity of the proposed method is verified through some experiments.