A treatment system that applies energy to a living tissue to treat the same, the treatment system includes a sealing member which joins desired sealed regions of at least two living tissues when the energy is applied to the living tissues in a state where the desired regions are sealed, a maintaining member which maintains living tissues near the sealed regions in a contact state when the energy is applied to the living tissues in a state where the tissues near the regions sealed by the sealing member are in contact with each other, at least one first control section which controls an output of the energy that is applied to the sealing member, and at least one second control section which controls an output of the energy that is applied to the maintaining member.