A1-Mg-Si series alloy plate excellent in thermal conductivity and strength, and method of manufacturing the same

An Al-Mg-Si series alloy ingot consisting essentially of Si: 0.2 to 0.8 wt %, Mg: 0.3 to 0.9 wt %, Fe: 0.5 wt % or less, Cu: 0.20 wt % or less and the balance being aluminum and inevitable impurities, or an Al-Mg-Si series alloy ingot consisting essentially of Si: 0.2 to 0.8 wt %, Mg: 0.3 to 0.9 wt %, Fe: 0.5 wt % or less, Cu: 0.20 wt % or less, Zn: 0.5 wt % or less and the balance being aluminum and inevitable impurities, is prepared. The alloy ingot is homogenized, then subjected to rough hot rolling and finish hot rolling, and finally to cold rolling. One of plural passes performed at the rough hot rolling is controlled such that material temperature immediately before the aforementioned one of passes is from 350 to 440 ° C., cooling rate during the aforementioned one of plural passes is 50° C./min or more, material temperature immediately after the aforementioned one of passes is from 250 to 340° C. and plate thickness immediately after the aforementioned passes is 15 mm or less. The cold rolling is controlled such that rolling reduction is 30% or more. Furthermore, the cold rolled plate is subjected to final aging at a temperature of 180° C. or below, or is not subjected to final aging.