CUTTING INSERT AND REPLACEABLE-EDGE ROTARY CUTTING TOOL

A cutting insert is provided in which, while a bottom surface thereof has an inclined surface, high strength is attained around a screw hole of the bottom surface. A cutting insert 1 according to the present invention is provided with a mounting hole 5 which penetrates a first end surface 2 and a second end surface 3, and cutting edges 8, 9, 10 are formed on an intersecting edge between the first end surface 2 and a peripheral side surface 4. The second end surface 3 has an inclined part 3a, and when a virtual plane P1, which is substantially perpendicular to an axis O and passes through any point of the cutting edges 8, 9, 10, is defined, the inclined part 3a is inclined so as to be more distant from the virtual plane P1, heading from the peripheral side surface 4 to the axis O. A projected part 5b projected in a direction along the axis O is formed in an area around the mounting hole 5 in the inclined part 3a.