A cutting insert including a surface involved in cutting, for which a cutting tool material composed of one of cBN based sintered body, ceramics, and cermet is used, the cutting insert comprising: a flank face; a nose R portion; a rake face having a positive rake angle; and a negative land with unequal width disposed between the rake face and the flank face, wherein a radius of the nose R portion is 0.4 mm or greater and 2.4 mm or less, an apex angle α of the nose R portion is 30° or greater and 95° or less, a rake angle β at a position of a bisecting plane of the apex angle of the nose R portion is 1° or greater and 10° or less, a ridge line where the negative land with unequal width and the rake face intersect and a ridge line where the negative land with unequal width and the flank face intersect are not parallel in plan view, and wherein a width W1 is 0.04 mm or greater and 0.2 mm or less, and Characterized in that at least on one side of the negative land with respect to a boundary which is an apex of a nose R portion cutting edge the width of the negative land with unequal width gradually decreases from the apex of the nose R portion cutting edge to a position at which the nose R portion cutting edge is connected to a linear cutting edge, and a ratio of the width W1 to the width W2 is 1.5 or greater wherein width W1 is the width of the negative land with unequal width in plan view at the apex of the nose R portion cutting edge, and width W2 is the width of the negative land with unequal width in plan view at the position at which the nose R portion cutting edge is connected to the linear cutting edge. a surface involved in cutting, for which a cutting tool material composed of one of cBN based sintered body, ceramics, and cermet is used, the cutting insert comprising: a flank face; a nose R portion; a rake face having a positive rake angle; and a negative land with unequal width disposed between the rake face and the flank face, wherein a radius of the nose R portion is 0.4 mm or greater and 2.4 mm or less, an apex angle α of the nose R portion is 30° or greater and 95° or less, a flank face; a nose R portion; a rake face having a positive rake angle; and a negative land with unequal width disposed between the rake face and the flank face, wherein a radius of the nose R portion is 0.4 mm or greater and 2.4 mm or less, an apex angle α of the nose R portion is 30° or greater and 95° or less, a rake angle β at a position of a bisecting plane of the apex angle of the nose R portion is 1° or greater and 10° or less, a ridge line where the negative land with unequal width and the rake face intersect and a ridge line where the negative land with unequal width and the flank face intersect are not parallel in plan view, and wherein a width W1 is 0.04 mm or greater and 0.2 mm or less, and Characterized in that at least on one side of the negative land with respect to a boundary which is an apex of a nose R portion cutting edge the width of the negative land with unequal width gradually decreases from the apex of the nose R portion cutting edge to a position at which the nose R portion cutting edge is connected to a linear cutting edge, and a ratio of the width W1 to the width W2 is 1.5 or greater wherein width W1 is the width of the negative land with unequal width in plan view at the apex of the nose R portion cutting edge, and width W2 is the width of the negative land with unequal width in plan view at the position at which the nose R portion cutting edge is connected to the linear cutting edge.