Drilling depth measuring device

The utility model relates to the technical field of depth measuring devices, in particular to a drill hole depth measuring device, which comprises a lifter, a drill hole extensometer probe and a drill hole extensometer, the positioning devices used for limiting the lifting position of the drilling elongation instrument probe are arranged on the surface of the drilling elongation instrument probe in a sleeving manner; by arranging the positioning device, when a worker needs to detect the depth of a drill hole, the worker only needs to lock an outer threaded pipe on the surface of a probe of the drill hole elongation instrument, then the worker can start a lifter, the lifter drives the probe of the drill hole elongation instrument to go deep into the drill hole, and the probe of the drill hole elongation instrument is driven by the lifter to go deep into the drill hole in the lifting process of the probe of the drill hole elongation instrument in the drill hole. The pulley can be always contacted with the inner