PURPOSE: To form a three-dimensional extruded stock having a hollow part and a solid part in the lengthwise direction by constituting the extruding die so that a hollow stock is subjected to extrusion forming in the case of a state that a male die and a female die are fitted deeply to each other, and a solid stock is subjected to extrusion forming in the case of a state that both of the dies are fitted shallowly to each other and a spacer is attached.

CONSTITUTION: The extruding die is provided with a female die 2 having a forming hole 20, and a male die 1 having a forming projecting part 6 which protrudes into the forming hole and forms a forming clearance against the inside of this forming hole. Both of the female and the male dies are combined in a fitted state like a die insert in such a form as they are approached and separated mutually in the extruding direction between a state the forming projecting part 6 advances into the forming hole, and a state that its part withdraws to the rear of the forming hole. In the state that the forming projecting part 6 retreats to the rear of the forming hole, a spacer 3 for holding a clearance interval is inserted and arranged so as to be attachable and detachable from the outside into a clearance formed between both the female and the male dies. In such a way, manufacture of three- dimensional extruded stocks whose transverse sections are different in the lengthwise direction can be realized, and also, a fitting work of the spacer, and a transverse section changing work of the extruded stock can be executed efficiently.