A preform main body of an iron species preform for forming a metal matrix composite inserted in an aluminum species alloy base material to be cast-in is bored with a first to fourth through holes communicating an inner peripheral face and an outer peripheral face. In a cast-in step, shrinkage in a peripheral direction of the inner peripheral face and the outer peripheral face of the iron species preform in accordance with solidification of the melted aluminum species alloy is uniformly received by shrinkage in accordance with solidification of the melted aluminum species alloy invading the through holes, movement thereof in the peripheral direction is restrained, a clearance can be prevented from being brought about at an interface, a cast-in performance is excellent and a stable bonding strength of the interface is achieved.