A wafer having a front face formed with a functional device is irradiated with laser light while positioning a light-converging point within the wafer with the rear face of the wafer acting as a laser light incident face, so as to generate multiphoton absorption, thereby forming a starting point region for cutting due to a molten processed region within the wafer along a line. According to one embodiment, an image is partitioned into regions, each of the regions having a discontinuity edge, a boundary, edge pixels along the boundary, and remaining pixels, and orientation of the discontinuity edge is estimated by computing a direction of least discrepancy within each of the regions by evaluating the edge pixels along the boundary of each of the regions. The conduction band sections are connected together in an electrically conductive manner by means of a connection part on the core near ends. The bend is less than ninety degrees from the long axis of the tube.