Provided is a charged particle beam device which can specify a position of an initial core with high accuracy even when fine line and space patterns are formed by an SADP in plural times. The charged particle beam device includes a detector (810) which detects secondary charged particles discharged from a sample (807) when a charged particle beam is emitted to the sample having a plurality of patterns of line shape, a display unit (817) which displays image data of a surface of the sample on the basis of a signal of the secondary charged particles, a calculation unit (812) which calculates an LER value with respect to the plurality of the patterns of line shape from the image data, and a determination unit (816) which compares the values to determine a position of the initial core.