With regard to an Al—Cr—Zr based alloy having annealing temper, a high temperature strength at 180 to 200 degrees C. is ensured. An aluminum alloy for a plain bearing having improved fatigue resistance is to be provided. An aluminum alloy for a plain bearing solving the problems has a composition of 3 to 7 mass % Mg, 0.1 to 0.3 mass % Cr, and 0.1 to 0.3 mass % Zr, with the balance being Al and inevitable impurities. A principal structure of the aluminum alloy consist of an Al matrix containing solute Mg, minute particles of Cr, and Zr.