PURPOSE: To easily form and to reduce the production cost by utilizing a softened state directly after extruding an aluminium material, and realizing forming at prescribed intervals in the extruding direction at the same time with the extruding process.

CONSTITUTION: An aluminum forming material 7 having a required cross-sectional shape is extruded from an extruding die 5, a forming die 13 is pressed to the forming mateiral 7 at a position to keep the softened state just after being extruded, and the forming material 7 is press-formed at prescribed intervals in the extruding direction. A supporting member 9 to abut onto the forming material 7 is installed on the neighborhood of the extruding die 5. The forming die 13 to execute press-forming by holding the forming material 7 with the supporting member 9 in between and pressing the forming material 7 is installed oppositely to the supporting member 9.