Abstract: A mass flowmeter includes: a casing (18), two U-shaped measurement tubes (1, 2) with identical structures within the casing (18), a vibration exciter (3) installed at a center axis line of the two U-shaped measurement tubes (1, 2), two detectors (4, 5) respectively located at centers of second circular arc segments (22, 23), four distance plates (6, 7, 8, 9), two flanges (10, 11) respectively arranged at two outermost ends of the mass flowmeter symmetrically, two end connecting tubes (12, 13) connected to the U-shaped measurement tubes (1, 2) through two flow dividers (14, 15) which are connected to each other through an intermediate connecting tube (16), and a lead wire connector (17); wherein the two U-shaped measurement tubes (1, 2) are arranged in parallel, each of the U-shaped measurement tubes (1, 2) includes a first circular arc segment (19), wherein both sides of the first circular arc segment (19) are each connected to sloped tube segments (20, 21), the second circular arc segments (22, 23), and stra