A three-way indexable throwaway tip for deep-hole drilling can be used as a center cutting blade body for a drill head in either whole cutting type or uncut core break-off type applications. The throwaway tip for deep-hole drilling is of a thick plate body having a three-fold symmetry with three cutting sections that are rotationally spaced apart at a central angle of 120 degrees. When mounted on a drill head, one cutting section of the throwaway tip faces a drilling direction. The forward facing blade edge of that cutting section includes an inner blade edge shorter in blade length and an outer blade edge longer in blade length forming an apex. The outer blade edge is composed of two consecutive blade edge portions of a peak-side outer blade edge portion having a smaller outer blade edge angle and a corner-side outer blade edge portion having a larger outer blade edge angle.