An adjustable attenuation adapter mainly comprises a fixing body having a bore centrally disposed therethrough and a connecting member extending outwardly from the bore; a moving body having a cylindrical body with a threaded outer surface; an inner roller being disposed within the central bore of the fixing body, the inner roller having an outer surface with gear teeth and an inner threaded surface for driving the threaded outer surface of the cylindrical body of the moving body; and an adjusting knob disposed within the fixing body and adjacent to the inner roller, the adjusting knob having a gear body for driving gear teeth of the inner roller. Since the threaded outer surface of the cylindrical body is threadedly driven by the inner threaded surface of the inner roller which is also gearedly rotated by the adjusting knob, the rotation of the adjusting knob causes the axial displacement of the moving body with respect to the fixing body.