To provide a method for specifying a magnetic flux concentrating part of a perpendicular magnetic recording head capable of accurately and surely specifying the magnetic flux concentrating part on the perpendicular magnetic recording head, where the ATI is generated.

A writing is carried out into a track on a perpendicular magnetic recording medium by using the perpendicular magnetic recording head, and a start point or end point of the writing is detected on this perpendicular magnetic recording medium, and the start position or end position of the generation of ATI on the perpendicular magnetic recording medium is detected on the basis of the detected start point or end point, and from the detected start position or end position of the generation of ATI with respect to the detected start point or end point, the magnetic flux concentrating part of the perpendicular magnetic recording head is detected, where the ATI is generated.