To provide an inexpensive screw torque measuring device and a screw torque measuring method, whereby a torque gradient curve is more accurately drawn.

The inside of this torque measuring device 1 comprises a gear part 2 having an approximately cylindrical main body 2a, a worm gear and the like and an input shaft 2c at a right side face of the main body, a light shielding plate 8 mounted through the input shaft, and a gear accommodating member 2b holding the light shielding plate and including an optical sensor 9, a rectangular main body part 5 in which the gear part is installed, a supporting part 3 for fixing a screw 10 and the like at an upper part of the main body part and having a torque detector 11 for detecting the screw torque on its central part, and a handle 7 for applying the torque to a screw and the like from the input shaft. The device further comprises a measuring apparatus 6 for detecting the screw torque from the light shielding plate and the like of the gear part by rotating the handle, connecting the detected screw torque from the main body part by the first cable 6a, and outputting the torque gradient curve and the like.