PURPOSE: To set an optimum machining route on a unspecified work and to utilize other device as a part of a continuous machining system during the single use of a machining device by a method wherein a plurality of tool automatic exchange type machining devices and placing parts are mounted in juxtaposition on a machining route, and two or more robots are movably mounted along the route.

CONSTITUTION: When machining contents A and B are applied on a work 2, the work 2 is carried in from a placing part 41 and fed to machining devices 31 and 32 by means of a robot 51. The machining content A is applied thereon by means of a tool 38 in a horizontal direction and fed in an intermediate placing part 42. Orientation of the work 2 is changed by the placing part 42 and red to machining devices 33 and 34 by means of a robot 52, After the machining content B is machined, the work is fed to a placing part 43 by means of the robot 52 again and carried out to a next process. When the machining device 31 is removed from a control system and machining of the particular work 2 is effected independently, other work 2 is carried from a placing part 41. After the work is fed to the machining device 32 by the robot 51 for machining A, the machining B is applied by means of the machining devices 33 and 34, and thereafter the work is discharged from the placing part 43.