Indexable cutting tool

An indexable cutting tool comprising a positive round insert that is mounted to a support seat provided at a periphery of an end of a tool body,

• wherein a positioning section that positions a cutting edge, used in cutting, at an indexed point is provided at a portion of the round insert towards a bottom surface at a periphery of the round insert,
• wherein the support seat includes a first seat side surface, a second seat side surface, and a restraining section, the first seat side surface and the second seat side surface contacting and supporting side surfaces of the round insert that are disposed 90 degrees apart from each other, the positioning section of the round insert being fitted to the restraining section by bumpy portion fitting,
• wherein only one restraining section is provided between the seat bottom surface and the first seat side surface of the support seat,
• wherein a first relief portion is provided at a corner at a side of the first seat side surface, and a second relief portion that is larger than the first relief portion is provided at a corner at a side of the second seat side surface, and
• wherein, in a view perpendicular to a threaded hole formed in the seat bottom surface, the first relief portion has a first radius and the second relief portion has a second radius, and the second radius is larger than the first radius.