To provide a fillet roll machining machine suppressing deformation of a work, and capable of executing fillet roll machining by a desired roll pressure.

This machine has a rotation center 7 of a tail stock 6 supporting the tip of the crankshaft W; a head stock 20 grasping and rotationally driving a base end side work retention part of the crankshaft W by a chuck mechanism; a fillet roll 73 supported by a fillet roll jig 75, applying the fillet roll machining to a corner part R of a journal formed near the base end; a grasp roll 74 supported by a grasp roll jig 75 and pressed to the journal, cooperating with the fillet roll 73 to clamp the journal; and a backup plate face 58 provided in the head stock 20, abutting on a side face 75a of the fillet roll jig 75 on the head stock side.