There is provided an arrangement for driving reciprocating members, which is for use in the optical system of an electrophotographic copying machine of the scanning exposure type. The optical system is actuated to have an initial velocity through the resilient force caused by each of spring members subsequent to alternate arrivals to respective end positions of scanning and returning movements. After having obtained the predetermined velocity either for the scanning, or the return operation, the optical system is actuated to be electrically driven for the purpose through the actuation of a clutch.