In order to evaluate the cooling performance of cutting oil, cooling water, and the like more accurately than conventional means, there are provided a temperature measurement method and a temperature measurement device that can actually ascertain the temperature of a rotating tool such as a cutting tool during cutting or welding torch during welding in real time. The temperature measurement method uses a rotating holder that is rotatable around a rotating axis and has a hollow hole extending from a front end to a rear end along the rotating axis, and a rotating tool that is connected to the rotating holder and has a coaxial through hole with the hollow hole. In the temperature measurement method, a step of attaching a temperature measurement unit near the through hole of the rotating tool, a step of measuring the temperature of the rotating tool that rotates coaxially with the rotating holder using the temperature measurement unit, and a step of receiving a measurement result of the temperature measurement unit by an electronic substrate are performed in this order.