A hot-wire cutter includes a frame, a tank supported on the frame, a first working head located on a floor of the tank, a second working head movably supported on the frame, a supporting unit supported on the frame and used to support an annular work piece, a restraining unit supported on the frame and used to clamp the annular work piece, and a rotating unit supported on the frame and used to rotate the annular work piece. Thus, a line between the first and second working heads is directed through the centers of initial apertures in the annular work piece, one after another, to facilitate precise processing of sections of the annular work piece corresponding to the initial apertures.