The utility model discloses a belt pulley deviation measuring device, include: calibrated scale and two laser emission devices, two laser emission devices set up respectively on two belt pulleys of beam -pumping unit, the calibrated scale sets up two on the beam -pumping unit basis between the belt pulley, two the laser ray of laser emission device transmission all shows on the calibrated scale. The utility model discloses set up a laser emission device on every belt pulley of beam -pumping unit, can accurate instruction belt pulley spatial position through the laser ray that shows the transmission of laser emission device on the calibrated scale to carrying out the accurate measurement to two belt pulley displacements, and carrying out the belt pulley position according to measuring result and correct, measuring result is accurate, and the scale on the calibrated scale makes things convenient for the reading, the utility model discloses simple structure, it is safe in utilization, convenient operation, the cost is lower.