Abstract: A plastic dryer has a drying tank provided with a magnetic control tube in the interior. The magnetic control tube is connected with a connecting tube, which has one end installed with an air filter having a wind inlet and the other end connected with a wind duct, which is connected with a windmill. Thus, microwave heating of the magnetic control tube is able to vaporize the water molecule of the plastic in the drying tank and dry it up with quickness, able to economize time and electricity and having excellent effect in drying plastic. The dried plastic is used for injecting molding by an injection-molding machine.