PURPOSE: To measure the height of the suspended trolley wire for electric railroads from the rails and the displaced position from the center of the rails accurately and simply.

CONSTITUTION: This apparatus is constituted of a main body 1 of an measuring instrument stage, which is mounted on rails and can be moved and stopped, and a main body A of a measuring instrument, which is provided on the main body 1 of the measuring instrument stage so that the moving adjustment in the lateral direction in the measurement of a nullified-length trolley wire can be performed. In the case of the main body A of the measuring instrument, a guide rail 8, which is arranged in the longitudinal direction, a vertical laser light device 9, which is guided and moved with the guide rail 8, and a slant laser light device 10 are provided. Thus, the displaced position and the height of the suspended trolley wire can be measured accurately and simply.