Abstract: A reamer includes a column section rotating around a central line in a predetermined rotation direction; a blade section provided on an outer surface of the column section and extending while being twisted in a direction to upper-cut; a cut liquid flow passage provided in the column section to introduce a cut liquid into the cut liquid flow passage; and an outlet group formed on the outer surface of the column section and connected with the cut liquid flow passage. The cut liquid flow passage extends such that the cut liquid is discharged from the outlet group toward a back portion of the reamer.