A method of machining a crankshaft from a workpiece whereby all of pin and journal portions of the workpiece are milled and thereby machined with a single crankshaft miller unit. The method comprises: establishing a phase position of the workpiece (3) with a phase positioning jaw (4c) that is provided in one of the chucks (4); clamping the workpiece (3) at its opposed ends with both the chucks (4); milling with a cutter (5e), thereby machining journal and pin portions of the workpiece (3) in succession; after all of the journal and pin portions are milled in the workpiece (3) except a first journal portion (J1) that is located at a position where the phase positioning jaw (4c) and the cutter (5e) may interfere with each other, unclamping the one chuck (4) provided with the phase positioning jaw (4c) and retracting that one chuck (4) to a position at which the jaw (4c) and the cutter (5e) may no longer interfere with each other; clamping again the workpiece (3) at its opposed ends with both the chucks (4); and thereafter milling and thereby machining the first journal portion (J1) with the cutter (5e).