Disclosed is a preparation method for a composite which comprises the following steps: (a) preparing unit metal pieces comprising two or more types of different metals; (b) circumferentially arranging the two or more types of unit metal pieces in a mold comprising upper and lower dies; (c) applying compressive stress to the loaded metal pieces using the upper and lower dies; and (d) rotating the upper and lower dies in one or two directions to apply torque in the pressed state.