To provide a shaftlike workpiece machined state detecting device capable of positively detecting the machined state of a shaftlike workpiece while reducing cost.

A crankshaft 12 is positioned by clamp mechanism 6, axial positioning mechanism 42 and pressing mechanism 44. A detecting pin 76 of a first detecting mechanism 70 is inserted in a key groove 154, and the end of a rotating member 74 approaches a proximity sensor 84a to detect the key groove 154. A detecting pin 114 of second detecting mechanism 104 is inserted in a key groove 156, and a plate member 112 approaches a proximity sensor 116a to detect the key groove 156. It can therefore be judged that the key groove 154 and the key groove 156 are formed satisfactorily.