A treatment device treats a biotissue by heating the biotissue to a target temperature. The device includes a heat-transfer member conveying heat to the biotissue, a heat-generating chip including a heat-generating member, a first temperature-measuring module, a temperature-measuring element disposed on the heat-transfer member, a second temperature-measuring module, and a controller. The heat-generating member heats the heat-transfer member. The first temperature-measuring module obtains a first temperature of the heat-generating member. The second temperature-measuring module obtains a second temperature measured by the temperature-measuring element. The controller determines the supplied electric power based on the first temperature after start of heating and before a transition point in time, and based on the second temperature after the transition point in time.
