Abstract: A method and an apparatus for ordering a working operation in an assembly line having sublines in which parts for different models are assembled. All of the parts in the assembly line have serial numbers. The parts are allocated with a working code which comprises a sub-serial number, a line code and a model code. The sub-serial numbers are successive numbers within each sub-line. The line code indicate the sub-line in which the part is manufactured, and the model code indicates the working operation to be performed in each line according to the model. The working code is transmitted into a working order instructing apparatus by which the working code is instructed. When the sub-serial numbers of the working code are consecutive in the sub-line, it is determined that the working operation designated by the working code should be performed.