A manufacturing apparatus for processing a forged blank from which flash has been removed, in a process of manufacturing a forged crankshaft including journals serving as an axis of rotation, pins decentered from the journals, and crank arms connecting the journals and the pins, wherein: the forged crankshaft further includes one or more counterweights integrated with one or more of the crank arms; the forged blank includes rough journals (J'), rough pins (P'), rough crank arms (A') and rough counterweights (W') corresponding to the journals, the pins, the crank arms and the counterweights, respectively, of the forged crankshaft; and at least one of the rough crank arms (A') includes a first excess portion (Aaa, Aba) protruding from a side portion in a region near an adjacent one of the rough pins (Aa', Ab'); the manufacturing apparatus comprising: a pair of upper and lower dies capable of deforming the first excess portion (Aaa, Aba) and thereby thickening the side portion of the rough crank arm (A') including the first excess portion (Aaa, Aba) in the region near the adjacent rough pin (Aa', Ab'); and a first tool fitted in an open space made in the pair of dies, the first tool capable of coming into contact with a rough-journal-facing surface (As) of the rough crank arm (A') including the first excess portion (Aaa, Aba), except the side portion in the region near the adjacent rough pin (Aa', Ab'), wherein: the pair of dies and the first tool have first guides (10d, 20e) to guide the first tool from a retracting position to a contacting position; characterised in that the first guide(s) of the first tool is/are disposed on at least one of an upper surface and a lower surface of the first tool. the forged crankshaft further includes one or more counterweights integrated with one or more of the crank arms; the forged blank includes rough journals (J'), rough pins (P'), rough crank arms (A') and rough counterweights (W') corresponding to the journals, the pins, the crank arms and the counterweights, respectively, of the forged crankshaft; and at least one of the rough crank arms (A') includes a first excess portion (Aaa, Aba) protruding from a side portion in a region near an adjacent one of the rough pins (Aa', Ab'); the manufacturing apparatus comprising: a pair of upper and lower dies capable of deforming the first excess portion (Aaa, Aba) and thereby thickening the side portion of the rough crank arm (A') including the first excess portion (Aaa, Aba) in the region near the adjacent rough pin (Aa', Ab'); and a first tool fitted in an open space made in the pair of dies, the first tool capable of coming into contact with a rough-journal-facing surface (As) of the rough crank arm (A') including the first excess portion (Aaa, Aba), except the side portion in the region near the adjacent rough pin (Aa', Ab'), wherein: the pair of dies and the first tool have first guides (10d, 20e) to guide the first tool from a retracting position to a contacting position; characterised in that the first guide(s) of the first tool is/are disposed on at least one of an upper surface and a lower surface of the first tool. a pair of upper and lower dies capable of deforming the first excess portion (Aaa, Aba) and thereby thickening the side portion of the rough crank arm (A') including the first excess portion (Aaa, Aba) in the region near the adjacent rough pin (Aa', Ab'); and a first tool fitted in an open space made in the pair of dies, the first tool capable of coming into contact with a rough-journal-facing surface (As) of the rough crank arm (A') including the first excess portion (Aaa, Aba), except the side portion in the region near the adjacent rough pin (Aa', Ab'), wherein: the pair of dies and the first tool have first guides (10d, 20e) to guide the first tool from a retracting position to a contacting position; characterised in that the first guide(s) of the first tool is/are disposed on at least one of an upper surface and a lower surface of the first tool. the pair of dies and the first tool have first guides (10d, 20e) to guide the first tool from a retracting position to a contacting position; characterised in that the first guide(s) of the first tool is/are disposed on at least one of an upper surface and a lower surface of the first tool.