Metal joined body and production method therefor

A metal joined body comprising an iron base body and an aluminum base body that are joined together via a joint layer,

• the joint layer having a first layer composed of a first intermetallic compound formed on the iron base body side and a second layer composed of a second intermetallic compound formed on the aluminum base body side,
• the first layer having a plurality of elongated pile-shaped first protrusions that merge integrally into the iron base body and extend from the iron base body into the first intermetallic compound, the plurality of elongated pile-shaped first protrusions being approximately uniformly distributed in the first intermetallic compound and forming an interface between the iron base body and the first layer of the joint layer, wherein
• the first protrusions comprise 10 to 55 protrusions per a reference length (50 μm) of the first layer, and
• at least some of the plurality of elongated pile-shaped first protrusions extend at least halfway into a thickness of the first layer of the joint layer.