PURPOSE: To simply and easily proceed to finish-machining in a short time after a rough or a medium machining by setting up the height of a frame body whose flat surface shape is larger than that of a workpiece to be machined to be up to the position of an electrode arrangedly provided 011 the workpiece to be machined.

CONSTITUTION: A frame body 6 inside which a workpiece 9 to be machined is ready for being positioned is set on a work table 4, and the frame body 6 is composed so that its height may be up to the position of an electrode 10 arrangedly provided on the workpiece 9. After a rough or a medium machining, the frame body 6 is laterally moved according to the selection of the movement of the frame body 6 and a position where it will move for forming a new processing bath of the frame body 6 and the work table 4. Electric discharge machining liquid 20 mixed with powder is charged in the above processing bath, and the workpiece 9 is finish-machined in the powder mixed electrical discharge machining liquid 20.