A manufacturing method for seamless manmade leather ball, wherein composites such as soft bioplastic resin or manmade leather, etc are injected, extruded or hot compressed to form upper and lower half bowl type thin covers to completely matchingly sleeve and sphere the corresponding ball bladder, next it is pressingly combined in the one step or two steps curing molds to fusionly paste with the reinforcement layer on said ball bladder to become an initial blank with waterproof layer which is further pressingly combined and cooled down to a fixed form in another set of forming molds with its outside surface formed with pre-formed lines and is further treated with a surface cortex layer and put in forming molds once again allowing surface decorative lines to be pressingly combined at second time, thereby allowing the ball to appear a better simulated leather ball outlook.