The fellowship boiler starts. Reconciliation of the present boiler is designed, by burning the harmony as a harmonious thermal oil boiler to raise the temperature of the cylindrical combustion chamber which is installed in a horizontal direction within the housing and having an inlet and reconciled to a side opening door; A first circulation path and the gap keeping the upper surface of the combustion chamber is arranged on the upper side of the combustion chamber to the combustion chamber and parallel to, the one side in communication with the combustion chamber by the other side and a lower passage; Maintaining the upper surface and the distance of the first circulation path by being disposed on the upper side of the first circulation path so as to be parallel with the first circulation path, one side is in communication by the other side with the upper passage of the first circulation passage the combustion chamber and the first circulation path second circulation passage for guiding circulation of the exhaust gas of high temperature, with a zigzag; The combustion chamber so as to surround the combustion chamber, the first circulation path and the second circulation path being formed between the first circulation path and the second circulation path and the inner wall of the housing, a heating medium having a loss of the heat medium and useful chulsugu ipsugu; And is formed into a predetermined plate structure of the hollow has a thickness space heating rapidly the inside is formed, one side of the top surface part is in communication with the combustion chamber upper side heating medium loss area and the upper connector, the other two sides addition of the combustion chamber both sides thermal loss are respectively communicated by the region and the side connecting pipe while the respective sides passing through the heat medium oil wherein the rapid heating space flows into the connection pipe after the rapidly heated by the flame through the upper connector to be moved by the heat medium lost to be characterized by comprising a rapid heating. According to the present invention, to be able to be relatively small rapid heating space heating medium oil quickly heated flows as compared with the heating medium lost to the combustion chamber of the reconciled boiler heated so to rapidly increase the thermal oil temperature that can improve the thermal efficiency of the reconciled and, also to aid the rapid heating portion it may be vertically provided by being heated to add a thermal oil temperature to be able to recover heat from exhaust gas discharged to the exhaust port in each circulation path, and finally recovering the heat of exhaust gas discharged in it is possible to improve significantly the thermal energy utilization of reconciliation.