An apparatus for measuring a displacement of a railroad includes a pair of rail fixing members 100 fixed to enclose a lower part of one rail 10, and installed to be spaced from each other; a lengthwise sensor casing 200a installed between the pair of rail fixing members 100; and an angle sensor installed at the lengthwise sensor casing 200a so as to measure a change of an angle between the pair of rail fixing members 100. With such a configuration, the present invention can be applied to a structure of railroad ties formed of a concrete material. Further, data can be obtained with high reliability, since a displacement of the rail is directly measured.