A device (1) for ensuring continuous circulation in well drilling includes a tubular body (2), having an axial channel (2) with a lateral opening (3) which is closed by a removable plug (5). A tubular support (9) is placed in the axial conduit and supports a shut-off member (6) which is held in position by a retainer (14). The device (1) has an adjustment ring nut (50) which exerts a pressing action between the retainer (14) and the tubular support (9) to force the tubular support (9) in an axial limit-stop position against respective positioning and centering elements (11), to allow recovery of clearances during placement of the tubular support (9) and the valve (6) supported the tubular support inside the tubular body (2).