Measurement device

A measurement device that measures a target to be machined by a machine tool as a measurement target, comprising:

• an ultrasonic vibrator that emits an ultrasonic wave to the measurement target, which is reflected and/or diffracted from the measurement target,
• an acoustic lens that focuses the reflected and/or diffracted wave,
• a sound-receiving element unit that converts the ultrasonic wave focused by the acoustic lens to an analog electrical signal;
• an A/D converter unit that converts the analog signal from the sound-receiving element unit to a digital signal;
• a calculator connected to the A/D converter unit;
• a numerical controller that gives a command about a machining shape;
• and
• a driving mechanism that makes the ultrasonic vibrator, the acoustic lens, and the sound-receiving element unit move and tilt relative to the measurement target in response to the machining shape acquired from the numerical controller, wherein
• the calculator stores information in chronological order acquired by the sound-receiving element unit through scanning irradiation with the ultrasonic wave, converts the information stored in chronological order to space information, and acquires an acoustic intensity distribution.