An aluminum alloy includes: a core material made of an aluminum alloy including Si, Cu, and Mn, with the balance being Al and unavoidable impurities; a brazing material cladded onto one side surface of the core material, and made of an aluminum alloy including Si, with the balance being Al and unavoidable impurities; and a sacrificial anode material cladded onto the other side surface of the core material, and made of an aluminum alloy including Zn and Si, with the balance being Al and unavoidable impurities, wherein a total number density of single phase pure Si and a intermetallic compound existing in the sacrificial anode material and having a grain size of 0.1 μm or more and 1.0 μm or less is 1×103/mm2 or more and 1×106/mm2 or less.