An aluminum alloy heat exchanger having a tube composed of a thin aluminum alloy clad material, wherein, in the clad material, one face of an aluminum alloy core material containing Si 0.05 1.0 mass % is clad with an Al--Si-series filler material containing Si 5 20 mass %, and the other face is clad with a sacrificial material containing Zn 2 10 mass % and/or Mg 1 5 mass %, and wherein an element diffusion profile of the clad material by EPMA satisfies (1) and/or (2): L-L.sub.Si-L.sub.Zn.gtoreq.40(.mu.m) (1) L-L.sub.Si-L.sub.Mg.gtoreq.5(.mu.m) (2) wherein L is a tube wall thickness (.mu.m); L.sub.Si is a position (.mu.m) indicating an amount of Si diffused from the filler material; and L.sub.Zn and L.sub.Mg each represent a region (.mu.m) indicating an amount of Zn or Mg diffused from the sacrificial material, respectively; and a method of producing the heat exchanger.