The invention relates to an underwater verticality adjustment device of an acoustic Doppler current profile (ADCP) sensor, and belongs to the field of hydrologic monitoring. A worm and gear speed changing box is fixedly arranged on a fixed framework which is fixed on a prefabricated foundation, a sleeve of a rocker arm mechanism is in clearance fit with a worm-wheel shaft of the worm and gear speed changing box, a cross axle adjustment mechanism is installed on the fixed framework, the ADCP sensor is arranged on the cross axle adjustment mechanism and is fixedly connected with a linear bearing and a guide rod mechanism of the linear bearing, one end of a transmission mechanism 7 abuts against the sleeve of the rocker arm mechanism, the other end of the transmission mechanism is connected with the linear bearing and the guide rod mechanism of the linear bearing, and the worm and gear speed changing box and the rocker arm mechanism are provided with tensioning mechanisms. The device has the advantages of being small in size, light in weight, precise in positioning, and convenient to install, adjust and maintain, and the like; adjustment stability in the horizontal direction and the vertical direction is good; and compared with the prior art, the device is precise in positioning, can guarantee completeness and reliability of hydrologic data collection, has a self-lock function, and is simple and novel in structure, convenient to use, and strong in practicability.