We have developed High-frequency linear friction welding (HFLFW) that works at 250 Hz, which is more than five times as high as the frequency of a conventional LFW process, aiming to weld high thermal conductivity materials such as aluminum alloys. The purpose of this study is to establish the fundamental HFLFW process for the welding of Al alloys. The mechanical properties and microstructure of the HFLFW joint were investigated for 6063 and 1050 Al alloys. Further, the characteristics of the process were clarified by the histories of temperature and amplitude. Sound welds were achieved for 6063 Al alloy, while 1050 Al alloy could not be welded successfully because of the extra-low mechanical property. The rise in temperature temporarily stopped at initial phase because HFLFW machine that used electromagnetic force to realize working at a high frequency had less shear power than a conventional LFW that used hydraulic motor. It was found that welding with a lower pressure was effective to improve the process. HFLFW is a promising process for the welding of precipitation-hardening aluminum alloys owing to the less heat effect during the process.