PURPOSE: To provide an internal abrading tool and its manufacturing method capable of bringing filaments into contact with the inner face of a workpiece as widely as possible, and applying an abrasive to the workpiece as much as possible.

CONSTITUTION: This internal abrading tool is constituted of a tool shaft 20 and filaments 21, 23 protruded in the radial direction from the tool shaft 20 and containing an abrasive, and the filaments 21, 23 are curved into an arc shape having components in the axial direction and peripheral direction. In manufacturing this tool, the tool protruded with the filaments 21, 23 in the radial direction from the tool shaft 20 is forcefully inserted into the cavities 31, 32 of a mold 30 having the outer diameter smaller than that of the tool, then the mold 30 is heated in a furnace, then it is quenched in a quenching tank. After the mold 30 is extracted from the quenching tank, the tool is removed from the mold 30.