The invention discloses a turning tool for regular polygon inner hole processing. The turning tool comprises a lathe; the lathe is provided with a chuck and a cutter rest that are arranged oppositely; the chuck is used for clamping a workpiece of which the processing end face faces towards the cutter rest; a circular bottom hole internally tangent to a designed regular polygon inner hole is formed in the processing end face of the workpiece; a guide block provided a linear type guide hole is arranged on the chuck; a cutter feeding mechanism is fixed to the cutter rest, and comprises a fixing component, a rotation component, a linear movement component and a conversion component; circumferential rotation of the chuck is transferred to a cam disc through a shifting rod of the rotation component, then circumferential rotation displacement is converted to linear displacement of the linear movement component by the cam disc through the conversion component, and a linear displacement cutter rod of the linear movement component drives a cutter to carry out turning processing of the regular polygon inner hole in the bottom hole in the workpiece. The turning tool has the characteristics of high processing precision, easy processing procedure, high processing efficiency, low labor intensity, low processing cost, and the like, and is reliable and practical.