A treatment system includes a seal member, a maintaining member and a control section, and is configured to exert energy to a living tissue to treat the living tissue. The seal member is configured to join a sealed region which seals desirable regions of at least two living tissues when the energy is exerted to the sealed region. The maintaining member is configured to maintain the living tissues in the vicinity of the sealed region being brought into contact with each other when the energy is exerted to the living tissues. The control section is configured to offset energy output timings of the seal member and the maintaining member.
