Abstract: A swing arm for actuating a magnetic head having a multiplicity of extremely thin blade of 0.9 mm in thickness that has been difficult to produce in a conventional casting may be produced by die-casting. Fixed cores and movable cores are disposed in a casting space provided in a parting line between a fixed core and a movable core. A body casting space and a blade casting space are set. A cross-sectional area of an overflow gate provided at an end of the blade casting space is greater than a cross-sectional area of a runner gate for connecting a runner and the body casting space. At the same time, a weight of the overflow material overflowed from the overflow gate to the molten material storage portion is set to be greater than a weight of a product portion filled in the casting space. The flow of the molten material to the blade casting space that is narrow is made smooth.