The invention discloses a measuring apparatus for vertical displacement of a bridge beam body. The measuring apparatus for the vertical displacement of the bridge beam body comprises a ruler body, a transverse rotating disc and a transverse positioning plate from top to bottom; the ruler body is fixed on the transverse rotating disc, and the transverse rotating disc is connected with the transverse positioning plate by virtue of a rotating shaft; and the ruler body, the transverse rotating disc and the rotating shaft are coaxial and can rotate relative to the axial direction of the transversepositioning plate. The transverse positioning plate provides a two-level axial rotation degree of freedom by adding a rubber strip, so that the installation condition of uneven bottom surfaces of different bridge bodies can be satisfied; and the ruler body is formed by connecting different numbers of ruler components, and the length of the ruler body can be adjusted according to different bridge types and the geographical environment. When in actual application, the measuring apparatus is integrally inversely fixed on the bottom surface of a beam body, and is convenient for rapidly and accurately measuring the vertical displacement of the beam body as a novel leveling staff. By adopting the measuring apparatus for the vertical displacement of the bridge beam body, the technical difficulties in the conventional measuring technology that the measuring and preparation time is long, an additional support is needed, the manpower requirement is high, and the error is large can be solved.