A manufacturing method and a manufacturing device for integrally forming a waterproof structure for a 3C electronic product, and the method includes the following steps: a. feeding a predetermined amount of a solid silicone raw material into a sprue; b. extruding the solid silicone raw material in the sprue, so that the solid silicone raw material flows into, through a silicone inlet channel, a waterproof structure cavity in a mold in which a product is placed; and c. heating the flowable solid silicone with a high temperature in the mold to have a vulcanization reaction, and finally to integrally form a silicone waterproof structure on the product. The waterproof structure is of a great waterproof performance, good material toughness, small wear when being used repeatedly, and great fatigue resistance.