CUTTING INSERT AND TURNING TOOL WITH SUCH A CUTTING INSERT

A cutting insert 2 includes an upper surface 6, a lower surface 7 on a side opposite to the upper surface 6, and a peripheral side surface 8 connecting the upper surface 6 and the lower surface 7. A cutting edge 61 is formed in at least a part of a first ridgeline 60 where the upper surface 6 and the peripheral side surface 8 intersect. At least one bottomed recess 10 recessed from the lower surface 7 to the upper surface 6 is formed in an outer peripheral portion of the lower surface 7. Each of the recesses 10 is formed in a substantially triangular shape having a first vertex P, a second vertex Q, and a third vertex R. The first vertex P and the second vertex Q are respectively positioned on a second ridgeline 70 where the lower surface 7 and the peripheral side surface 8 intersect. The third vertex R is positioned on the lower surface 7 and separated from the second ridgeline 70.