A connection device and method of manufacturing the same is provided. The connection device includes a housing that includes a first face, into which a plug is introduced, and a second face that is formed to be in contact with the first face, a connection hole that extends to the inside of the housing from the first face, an opening that extends from the first face to the second face to partially expose the connection hole on at least the second face, and a sealing member that is arranged on an outer peripheral surface of the housing to surround a region where the opening is formed. When mounted on the case member of the electronic device, the sealing member may form a dustproof and waterproof structure between the inner peripheral surface of the case member and the outer peripheral surface of the housing.