To provide a temperature-measuring device that has a simple configuration, obtains an accurate measurement result with improved reproducibility, and measures the temperature of a rotor without any contact.

A measuring device for measuring the temperature of a rotor 1 without any contact has a primary circuit 3, where an AC current is supplied, at a stator side, a secondary circuit 8 that opposes it at a rotor side. The secondary circuit 8 includes a resistor 10 with temperature dependency. When the rotor temperature changes, the resistance change of the resistor with temperature dependency is transferred to a primary circuit due to the operation of a transformer. A voltage change being generated accordingly can also be utilized to control the rotary speed of the rotor and/or other quantities. The coil of the primary circuit being arranged at the stator may form a one-piece unit along with the coil of a magnetic bearing. In that case, one core 12 is shared by both magnetic systems.