The invention relates to a connecting device for fluid circuits in column chromatography. To ensure an inert connection without dead volumes, the device comprises a glass or fused silica thick-wall body with an inner capillary channel connected to the outside through radial holes. In such holes, metal or fused silica capillaries are inserted and each fixed by means of a coupling carrying a capillary set screw and a coupling fixing screw, with said screws acting on opposite positions of said body wall.