A mass flowmeter (1) based on the Coriolis principle is disclosed whose susceptibility to disturbances originating from the conduit, such as vibrations of the conduit or wide pressure variations of the fluid, and to other disturbances, such as impacts on the casing (11), is greatly reduced by mechanical means. It has a fluid inlet (113) and a fluid outlet (114) which are connected with the conduit via the casing; a support base (12) disposed within the casing and connected with the casing via at least one mechanical damping element (13, 14) which is located on a nodal line of vibration (19) of the support base; a single measuring tube which is bent in a plane parallel to the support base and ends in the fluid inlet (113) and the fluid outlet (114), a portion of said measuring tube to be vibrated in a direction perpendicular to said plane being fixed to the support base by fixing means (121, 122) located in the areas of opposite edges of the support base, and two connecting portions (152, 153) of said measuring tube extending from the respective fixing means to the fluid inlet and the fluid outlet, respectively; a vibrator (16); and at least one respective sensor (17, 18) disposed near each of the fixing means for sensing the vibrations of the tube portion.