holders are at the delivery position thus the thirteen treated wafers can be collectively delivered to thirteen wafer support holders meanwhile the handling device 50 of the known art disclosed in for example japanese unexamined patent publication no h03 154791 is utilized and the illustration and description thereof will be thus omitted then the general operation of this carrying system will be described briefly 1 thirteen untreated wafers 22 are loaded on the intermediate cassette device 30 in the waiting state by the handling device 50 2 when the ion implantation is completed in the vacuum container 10 the main cassette device 20 to which the treated wafers 22 are shifted is raised from the vacuum container 10 3 to receive the treated wafers 22 the wafer unloading cassette device 40 is turned to the wafer delivery position 4 the main cassette device 20 is lowered by a given distance 10 mm here to deliver the treated wafers 22 to the wafer unloading cassette device 40 5 the wafer unloading cassette device 40 receives the treated wafers 22 and is turned to the original waiting position the treated wafers 22 are thus collectively carried out of the main cassette device 20 6 after the wafer unloading cassette device 40 is turned to the waiting position the intermediate cassette device 30 which is in the waiting state in 1 above is turned to the delivery position of the wafers 22 7 the main cassette device 20 is raised by 10 mm and receives the untreated wafers 22 from the intermediate cassette device 30 8.