A waterproof structure is used with a printed circuit board, which is primarily composed of an upper layer membrane, a lower layer membrane, and an insulation layer, which are conjoined to one another. Besides, at least one first channel and second channel are provided on the upper layer membrane and the lower layer membrane respectively and correspondingly. Also, a pressure-adjusting hole, whose periphery is larger than that of the first channel and the second channel, is provided on the insulation layer corresponding to the positions of the first channel and the second channel. After the first channel, the second channel, and the pressure-adjusting hole of the insulation layer have been conjoined, a waterproof unit will be formed at a place where the contact points of the three are not connected to one another. The waterproof unit contains circulated air and prevents moisture from permeating into the circuit board thereby avoiding a short circuit of the circuit board.