A coordinate measuring device includes a probe detecting a shape of a measured object and outputting a signal indicating results of the shape detection. A probe interface receives the signal indicating the results of the shape detection. A cable transmits the signal indicating the results of the shape detection between the probe and the probe interface and bends accompanying displacement of the probe. The probe interface includes an impedance detector having a calculator detecting impedance in the cable. The impedance detector transmits high-speed test data to the probe through the cable and detects impedance in the cable according to whether a reception confirmation signal output by the probe is received.