Cutting insert and gear cutter

A cutting insert which is a replaceable cutting insert fixed to a tool body and constituting a gear cutter, the cutting insert comprising:

• a first face which is a rake face, a second face on a side opposite to the first face, a peripheral side face connecting the first face and the second face, and a mounting hole provided in the peripheral side face, wherein
• a cutting blade is formed on a ridge line where the first face and the peripheral side face cross each other,
• the cutting blade includes a corner part that includes one end of the cutting blade and that is capable of machining a tooth bottom of a gear, and a main part extending to the corner part from the other end of the cutting blade on the side opposite to the one end,
• the peripheral side face includes an outer side face facing the cutting blade and an inner side face on a side opposite to the outer side face and in contact with the tool body, the outer side face further including a first flank facing the main part,
• the mounting hole penetrates the first flank and the inner side face so that a center axis of the mounting hole crosses the inner side face perpendicularly, and
• the cutting insert is formed having a wedge shape such that a thickness between the first flank and the inner side face continuously decreases along an entirety of the main part towards the other end.