PURPOSE: To obtain an extruded material excellent in dimensional accuracy by arranging a control die of a small reduction rate of area at the exit side and moving the die vertically with respect to an extrusion center line basing on the deviation of the detected dimension of extruded material at the exit side from its reference value.

CONSTITUTION: A control die 18 of a small reduction rate of area and a die holder 19 are provided to the exit side of an extrusion device 1, and hydraulic devices 21, 21' move vertically the die 18 and the holder 19 while interlinking themselves to each other. The 1st holder frame body 20 is provided with hydraulic devices 22, 22' and is laterally movable with respect to the 2nd holder frame body. A dimension detector 24 detects the dimension of an extruded material 2' to transmit a signal to a control arithmetic device 25, which operates the moving direction and quantity of the die 18 basing on the deviation of the detected value from its reference value. Based on the operated values, the devices 21, 22, etc. move the die 18 by a required quantity, and the extrusion of material 2' is correctingly controlled to obtain a product excellent in dimensional accuracy.