Provided is a measurement device including: an irradiation optical system which emits a primary charged quantum beam to a sample for scanning; a detector which detects secondary charged particles generated from the sample; and a signal processing unit which processes an output signal from the secondary charged particle detector which has detected the secondary charged particles, in which the signal processing unit includes a measurement unit which measures widths of a first pattern group calibrated with a well-known first dimension and a second pattern group calibrated with a well-known second dimension, and an operation unit which defines a relationship between the well-known dimensions of the first and second pattern groups and length measurement values of the first and second pattern groups as a function. Accordingly, it is possible to control device performance with high accuracy, by controlling a device state so that the measured value described above is within an acceptable range by comparing to a predetermined value provided in advance.