A treatment device for a medical treatment heats a biotissue. The device includes a treatment tool which includes a heat transfer portion and a resistance element, a storage section which stores a time-power list including time-power relations, and a controller. The controller includes a resistance value acquiring section acquiring a resistance value of the resistance element, a power supplying section supplying the power to the resistance element, and a control section. The control section causes the power supplying section to supply a predetermined state detection power in a state detection period, calculates a change of the resistance value in the state detection period, acquires the time-power relation corresponding to the change of the resistance value, and causes the power supplying section to supply the power based on the acquired time-power relation.
