A method of controlling the operation in a factory of an A.G.V. which automatically travels along a predetermined route consisting of a plurality of production lines having different line contacts and adapted to perform parts assembly or packaging. Optimum travel speeds with respect to all the lines are previously stored in the A.G.V. When the A.G.V. enters one of the production lines, it is instructed from the outside to travel constantly at a previously stored speed assigned to this production line. Thus, operations of the production line are successively performed.