Measurement device and measurement method

A measurement device comprising:

• an illumination optical system configured to apply illumination light to a target object;
• a detection optical system configured to make a detector detect return light from the target object based on the illumination light;
• a position control unit configured to control a height position, the height position being a relative position between the target object and a focusing point by the illumination optical system in a height direction;
• an acquisition unit configured to acquire, when a preparation sample is irradiated, at a predetermined position of the preparation sample, with the illumination light at a plurality of height positions different from each other, relationship information indicating a relationship between the height position and detected intensity based on a result of the detection of the return light by the detector, in which the preparation sample is the target object;
• and
• a measurement unit configured to obtain, by using the relationship information, surface height information at the plurality of measurement positions based on a test detection result, the test detection result being the result of the detection of the return light by the detector obtained when the illumination light is applied to the plurality of measurement positions on a test sample while setting the height position for the test sample to a predetermined reference position, in which the test sample is the target object.