Aluminum alloy forging

An aluminum alloy forging includes 0.30 mass % or more and 1.0 mass % or less of Cu; 0.63 mass % or more and 1.30 mass % or less of Mg; 0.45 mass % or more and 1.45 mass % or less of Si; the balance being Al and inevitable impurities, wherein the following relations are satisfied,[Mg content]×1.587≥−4.1×[Cu content]2+7.8×[Cu content]−1.9 (1)[Si content]×2.730≥−4.1×[Cu content]2+7.8×[Cu content]−1.9 (2)and the ratio of the integrated intensity Q1 of the X-ray diffraction peak of the CuAl2 phase to the integrated intensity Q2 of the X-ray diffraction peak of the (200) plane of the Al phase obtained by the X-ray diffraction method, Q1/Q2, is 2×10−1 or less.