Abstract: In a metal surface treatment apparatus in which a work article is immersed successively in a plurality of treatment tanks disposed in a line and containing respective treatment liquors, a traveling crane handling the work article in this operation is automatically controlled to travel over the tanks with a repeated horizontal speed pattern comprising an initial period of steady acceleration from the center of each tank, a period of high speed, and a period of deceleration upon approaching the center of the succeeding tank, at which the crane is stopped, and is automatically controlled to lower and raise the work article at the center of each tank with a vertical speed pattern comprising, in sequence, an initial period of descent at low speed, a period of high speed, a period of low speed as the lower end of the article approaches and enters the surface of the treatment liquor in the tank, a period of high speed, a period of low speed as the article approaches the lower limit of its descent, an initial period