A main magnetic pole layer is constructed so as to have a stacking structure in which a lower main magnetic pole layer having relative low saturated magnetic flux density and an exposed surface area is positioned on a leading side, and an upper main magnetic pole layer having relative high saturated magnetic flux density and having an exposed surface area is positioned on a trailing side. The exposed surface of a main magnetic pole layer has a planar shape of a bilaterally-symmetrical inverted trapezoidal shape in which a width of an upper edge is larger than a width of a lower edge and is equal to or larger than a width of the exposed surface of the main magnetic pole layer at an arbitrary intermediate position between the lower edge and the upper edge. In particular, a height at a center position in the exposed surface area in the upper main magnetic pole layer is larger than a height in the exposed surface area in an arbitrary peripheral position around the center point.