A medical device comprising: clamping means including a sticking member for sticking a biological tissue which lies at a periphery of a defect existing in a biological tissue and a sandwiching member for sandwiching said biological tissue so as to close said defect by cooperating with said sticking member; a catheter into which said sticking member and said sandwiching member are inserted; electric energy supply means for supplying electric energy to said sticking member and said sandwiching member of said clamping means; and a steering unit at hand mounted with a proximal portion of said catheter for steering said clamping means, wherein said medical device is configured for closing said defect by supplying electric energy from said electric energy supply means and by joining said biological tissues mutually in a state of sandwiching said biological tissue by said sticking member and said sandwiching member, characterised in that said steering unit at hand includes: contact members (84, 85) which are connected to the other terminal portions of conductive wires (d1, d2) whose one terminals (81, 83) are connected to said electric energy supply means and which are provided at mutually separated positions, terminals (81, 83) configured to be respectively positionable at respective steering-members which move said sticking member and said sandwiching member, and a control unit for on-off controlling the supply of said electric energy, wherein said respective terminals (81, 83) are configured to contact with said contact members (84, 85) respectively along with the move of said respective steering-members and wherein said medical device is also constituted so as to supply said electric energy to said biological tissue between said sticking member and sandwiching member by turning on said control unit. clamping means including a sticking member for sticking a biological tissue which lies at a periphery of a defect existing in a biological tissue and a sandwiching member for sandwiching said biological tissue so as to close said defect by cooperating with said sticking member; a catheter into which said sticking member and said sandwiching member are inserted; electric energy supply means for supplying electric energy to said sticking member and said sandwiching member of said clamping means; and a steering unit at hand mounted with a proximal portion of said catheter for steering said clamping means, wherein said medical device is configured for closing said defect by supplying electric energy from said electric energy supply means and by joining said biological tissues mutually in a state of sandwiching said biological tissue by said sticking member and said sandwiching member, characterised in that said steering unit at hand includes: contact members (84, 85) which are connected to the other terminal portions of conductive wires (d1, d2) whose one terminals (81, 83) are connected to said electric energy supply means and which are provided at mutually separated positions, terminals (81, 83) configured to be respectively positionable at respective steering-members which move said sticking member and said sandwiching member, and a control unit for on-off controlling the supply of said electric energy, wherein said respective terminals (81, 83) are configured to contact with said contact members (84, 85) respectively along with the move of said respective steering-members and wherein said medical device is also constituted so as to supply said electric energy to said biological tissue between said sticking member and sandwiching member by turning on said control unit. contact members (84, 85) which are connected to the other terminal portions of conductive wires (d1, d2) whose one terminals (81, 83) are connected to said electric energy supply means and which are provided at mutually separated positions, terminals (81, 83) configured to be respectively positionable at respective steering-members which move said sticking member and said sandwiching member, and a control unit for on-off controlling the supply of said electric energy, wherein said respective terminals (81, 83) are configured to contact with said contact members (84, 85) respectively along with the move of said respective steering-members and wherein said medical device is also constituted so as to supply said electric energy to said biological tissue between said sticking member and sandwiching member by turning on said control unit.