In order to achieve same level of high strength and ductility as 6061 aluminum forging alloy that is currently used for automobile applications, AZ31 magnesium alloy was subjected to ECAE processing, and the mechanical properties of the ECAE-processed specimens were investigated. Furthermore, automobile knuckle arm was produced by forging using the ECAE-processed material, and the mechanical properties of the forged product and their strain rate dependencies were investigated under impact tensile load conditions. As a result, 4pass-ECAE-processed specimen has fine and uniform microstructure and a texture whose basal planes are mainly parallel to the extrusion direction with some inclined at angles up to 450 to the extrusion direction. Therefore, they show high ductility even if the tensile direction is parallel to the extrusion direction. The knuckle arm forged using the ECAE-processed material exhibits high elongation even in the high strain rate region. Furthermore, the tensile strength, fracture elongation and absorption energy of the forged product increase with increasing strain rate and their values are higher than those of T6-treated 6061 aluminum forging alloy specified by JIS.