PURPOSE: To form a crank shaft at high accuracy by single full enclosed die forging die, by setting materials worked to correspond to the journal part and crank throw part in a pair of dies and pressing in a punch to the position of forming the crank throw part.

CONSTITUTION: A small diameter part (a) leaving working allowance and a large diameter part (b) to which metal of the same quantity or somewhat larger quantity than the crank throw part is given are formed on a billet 1 having the length of a crank shaft. The billet 1 is set in a pair of dies 2, 2' and clamped. When a punch 7 for forming the crank throw part is pressed in from outside of the dies 2, 2' to the large diameter part (b), pressed opposite part is formed by a pin 4a in the cavity 4, and overflowed part is put in the balance weight part 4c by backward extruding action and formed. By this way, a solid type crank shaft is formed finally.