A medical treatment device (12) to treat and join body tissues (L1, L2), includes at least a pair of holding members (52, 54) which is configured to hold the body tissues to be treated, an energy output portion (92, 94) which is provided in at least one of the pair of holding members, which is connected to an energy source (14) and which is configured to supply energy to the body tissues held by the pair of holding members, configured to join the body tissues and configured to form a joined portion, and a discharge portion (92a, 94a) which is configured to discharge a substance which prevents invasion of a fluid into the joined portion so as to cover a surface layer of the joined portion of the body tissues with the substance after the joined portion is formed.
