To provide a pattern measuring device and a pattern measuring method capable of discriminating a line from a space, when the line which is a measuring object and the space are formed approximately at equal intervals.

The pattern measuring device is equipped with a line profile creating unit for creating a line profile of a pattern formed on a sample by scanning with a charged particle beam, a differential profile creating unit for creating a quadratic differential profile by differentiating quadratically the line profile, and an edge detecting unit for determining whether an edge of the pattern is a rising edge or a falling edge from two peak positions and two peak values appearing in the vicinity of an edge position of the pattern obtained from the quadratic differential profile. Assuming that the two peak positions appearing in the vicinity of the edge position of the pattern obtained from the quadratic differential profile are defined as X1 and X2 (>X1), the edge detecting unit determines that the edge of the pattern is a rising edge when a signal amount of the peak position X1 is larger than a signal amount of the peak position X2.

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