Cutting insert and cutting tool with replaceable cutting edge

A cutting insert comprising:

• a first end surface and a second end surface at the opposite side to each other, each of the first end surface and the second end surface having a contour of substantial rotation symmetry around an axis (A) defined to extend through the first end surface and the second end surface, the contour of the first end surface and the contour of the second end surface being substantially plane-symmetrical about a median plane (M) which is defined to be perpendicular to the axis and bisect the cutting insert, each of the first end surface and the second end surface being configured in a way that raised corners and lowered corners are alternately positioned, and each of the lowered corners having an inner angle larger than that of the raised corner and being closer to the median plane than the raised corner;
• a peripheral side surface extending between the first end surface and the second end surface;
• at least three first cutting edge portions formed in an intersection ridge portion between the first end surface and the peripheral side surface, each including a corner cutting edge, a major cutting edge and a minor cutting edge in such a manner that the corner cutting edge extends along the related raised corner, the major cutting edge extends from one end portion of the corner cutting edge toward one lowered corner adjacent thereto, and the minor cutting edge extends from the other end portion of the corner cutting edge toward the other lowered corner adjacent thereto, wherein a distance between the raised corner and the one lowered corner between which the major cutting edge extends is longer than a distance between the raised corner and the other lowered corner between which the minor cutting edge extends, the major cutting edge has an inclined section closer to the median plane as a distance from the corner cutting edge is increased, and the minor cutting edge has an inclined section closer to the median plane as a distance from the corner cutting edge is increased;
• and
• at least three second cutting edge portions formed in an intersection ridge portion between the second end surface and the peripheral side surface, each including a corner cutting edge, a major cutting edge and a minor cutting edge in such a manner that the corner cutting edge extends along the related raised corner, the major cutting edge extends from one end portion of the corner cutting edge toward one lowered corner adjacent thereto, and the minor cutting edge extends from the other end portion of the corner cutting edge toward the other lowered corner adjacent thereto, wherein a distance between the raised corner and the one lowered corner between which the major cutting edge extends is longer than a distance between the raised corner and the other lowered corner between which the minor cutting edge extends, the major cutting edge has an inclined section closer to the median plane as a distance from the corner cutting edge is increased, and the minor cutting edge has an inclined section closer to the median plane as a distance from the corner cutting edge is increased.