A combined machining tool comprising: a shank that has its rear end to be mounted on a processing machine; a burnishing part that is arranged on the shank and burnishes an inner peripheral surface of a workpiece; and a reaming part that is arranged in front of the burnishing part and executes reaming wherein the burnishing part comprises: a mandrel that is fixed to the shank and has an outer peripheral surface na tapered shape; rollers that are arranged on the outer peripheral surface of the mandrel; a frame that holds the rollers so as to be rollable on the outer peripheral surface of the mandrel; an adjustment member that presses the frame axially from one end thereof to adjust its axial position with respect to the mandrel; and an elastic member that is arranged axially on the other side of the frame to support the frame, and characterised in that the reaming part comprises: a base part that is detachably attached to the mandrel; and a machining blade that is formed integrally with the base part, wherein a hole part is formed in the mandrel to have inside a tapered surface whose diameter decreases rearward, and a cylindrical part s formed in the base part so as to be fitted into the hole part, to have outside a tapered surface whose diameter decreases rearward, so that the diameter of the tapered surface of the hole part is smaller than that of the tapered surface of the cylindrical part, at an axial position where a stepped end face of the reaming part is aligned with the front end surface of the mandrel. a shank that has its rear end to be mounted on a processing machine; a burnishing part that is arranged on the shank and burnishes an inner peripheral surface of a workpiece; and a reaming part that is arranged in front of the burnishing part and executes reaming wherein the burnishing part comprises: a mandrel that is fixed to the shank and has an outer peripheral surface na tapered shape; rollers that are arranged on the outer peripheral surface of the mandrel; a frame that holds the rollers so as to be rollable on the outer peripheral surface of the mandrel; an adjustment member that presses the frame axially from one end thereof to adjust its axial position with respect to the mandrel; and an elastic member that is arranged axially on the other side of the frame to support the frame, and a mandrel that is fixed to the shank and has an outer peripheral surface na tapered shape; rollers that are arranged on the outer peripheral surface of the mandrel; a frame that holds the rollers so as to be rollable on the outer peripheral surface of the mandrel; an adjustment member that presses the frame axially from one end thereof to adjust its axial position with respect to the mandrel; and an elastic member that is arranged axially on the other side of the frame to support the frame, and characterised in that the reaming part comprises: a base part that is detachably attached to the mandrel; and a machining blade that is formed integrally with the base part, a base part that is detachably attached to the mandrel; and a machining blade that is formed integrally with the base part, wherein a hole part is formed in the mandrel to have inside a tapered surface whose diameter decreases rearward, and a cylindrical part s formed in the base part so as to be fitted into the hole part, to have outside a tapered surface whose diameter decreases rearward, so that the diameter of the tapered surface of the hole part is smaller than that of the tapered surface of the cylindrical part, at an axial position where a stepped end face of the reaming part is aligned with the front end surface of the mandrel.