To easily melt cut a thread securely preventing dust generation from the thread end, and preventing damage of cloth even if a heating element contacts cloth in unusing time by providing a switching means to energize the heating element by approaching each one end of the first and the second holders each other.

A spring 16 is fixed to each the other end of the first and the second holders 1, 11, and a predetermined clearance is secured between a thread receiver 15 and the heating element 7. A thread to be cut is positioned between both ends of a receiver 12. In the state shown in the figure a switching means 9 is in the OFF condition. The first and the second holders 1, 11 are grasped with a hand, and approaching the thread receiver 15 by the heating element 7 produces the ON condition by moving a contacting piece 9a which has been contacting the second holder 11 to heat up the heating element. The heating element 7 is made to approach the thread receiver 15 to nip the thread. Since a sewing thread used for dustproof clothes usually uses chemical fiber such as polyester, which melts at about 250°C, the nipped thread is heated to be cut easily.