A soldering iron having a soldering tip that melts solder at a distal end thereof comprising: a heater insertion fit portion which is a substantially cylindrical cavity opening at a proximal end of the soldering tip; a temperature sensor insertion fit portion which is a substantially cylindrical closed-end cavity in communication with a distal end of the heater insertion fit portion and has an internal diameter smaller than that of the heater insertion fit portion; a first cylindrical member which is disposed in the heater insertion fit portion and has an out diameter larger than the internal diameter of the temperature sensor insertion fit portion; a heater comprising a wire formed into a coil shape, a surface of the wire being covered with an insulating oxide film, the wire being fittingly inserted between an inner periphery of the heater insertion fit portion and an outer periphery of the first cylindrical member; a cable; and a temperature sensor which is connected to the cable, characterized in that the temperature sensor is disposed between an inner periphery of the temperature sensor insertion fit portion and an outer periphery of the second cylindrical member so as to be sandwiched therebetween, and contacts with the inner periphery of the temperature sensor insertion fit portion, further in that a second cylindrical member is provided and is substantially a cylindrical cavity disposed passing through the first cylindrical member and projects from a distal end of the first cylindrical member into the temperature sensor insertion fit portion, further in that the cable is disposed in the second cylindrical member so as to pass through the second cylindrical member. a heater insertion fit portion which is a substantially cylindrical cavity opening at a proximal end of the soldering tip; a temperature sensor insertion fit portion which is a substantially cylindrical closed-end cavity in communication with a distal end of the heater insertion fit portion and has an internal diameter smaller than that of the heater insertion fit portion; a first cylindrical member which is disposed in the heater insertion fit portion and has an out diameter larger than the internal diameter of the temperature sensor insertion fit portion; a heater comprising a wire formed into a coil shape, a surface of the wire being covered with an insulating oxide film, the wire being fittingly inserted between an inner periphery of the heater insertion fit portion and an outer periphery of the first cylindrical member; a cable; and a temperature sensor which is connected to the cable, characterized in that the temperature sensor is disposed between an inner periphery of the temperature sensor insertion fit portion and an outer periphery of the second cylindrical member so as to be sandwiched therebetween, and contacts with the inner periphery of the temperature sensor insertion fit portion, further in that a second cylindrical member is provided and is substantially a cylindrical cavity disposed passing through the first cylindrical member and projects from a distal end of the first cylindrical member into the temperature sensor insertion fit portion, further in that the cable is disposed in the second cylindrical member so as to pass through the second cylindrical member.