A tightening torque measuring unit capable of reducing errors with respect to either a clockwise or counterclockwise direction as soon as possible is provided. A tightening torque measuring unit 10, installed in a tightening device, includes a torque sensor 12 that detects a tightening torque and an amplifier that amplifies an output from the torque sensor 12. The amplifier 40 or 42 applies a different gain to the output from the torque sensor depending on whether the tightening direction of the tightening apparatus is clockwise or counterclockwise.