The invention relates to an electric double-layer capacitor and a manufacturing method thereof. A screen printing method is adopted to enable a conductive adhesive to be made into a circular conductive adhesive sheet with a certain diameter and a certain thickness, and then, the circular conductive adhesive sheet is transferred to an inner shell and an outer shell. Compared with an existing method of adopting a dispensor to inject the conductive adhesive to the inner shell and the outer shell, and then, adopting polarity electrodes to carry out flattening and shaping on the conductive adhesive, the method enables the conductive adhesive sheet prepared through the manufacturing method to be regular in shape and uniform in thickness; and the diameter of the conductive adhesive sheet can be designed to be in an optimum size. The prepared electric double-layer capacitor can work for 1000 hours under the temperature of 70 degrees and the voltage of 2.5V; the internal resistance increase rate of the double-layer capacitor is low; capacity reduction rate is low; and performance is more stable and reliable.