To provide a hot-working method for raising yield by preventing corner crack when a cast billet having a round cross section of a hard-to-work material, for example, SUS 303 of free-cutting steel which is obtained by vertical continuous casting method is made into an intermediate product by performing hot-working, that is, blooming and large size rolling.

When hot-working the round cast billet of the hard-to-work material which is cast by the vertical continuous casting method, by grasping the round cast billet (1) extracted from a heating furnace at one end with a manipulator (2), inserting it between a pair of round tups (3) having a radius slightly larger than the radius of the cast billet, lightly reducing the surface of the cast billet, turning it at an angle smaller than 90° around the axis and also repeating operations for feeding the cast billet by a distance not longer than the length of the round tup in the axial direction, an in-line press stage for adding plural times of reduction over the whole surface of the cast billet, reducing oscillation marks generated at casting and removing defects on the surface of the cast billet is inserted.