A fluid-tight housing device for a section of a handle device of an endoscope includes a housing. A housing opening is formed in the housing, and includes plural side edges and plural corner portions disposed between the side edges in a curved manner. A cover is secured to the housing, for closing the housing opening. A seal packing is squeezed between the housing and the cover. A first sealing lip is formed to project from an end of the seal packing, entered in the housing opening upon securing the cover to the housing, pushed on an inner surface of the housing, for sealing a joint thereof in a fluid-tight manner. A projection is formed on the cover in association with at least one of the corner portions, to project toward the housing, for pressing the seal packing to increase tightness of the first sealing lip.
