The difficult-to-work Mg alloys was subjected to equal channel angular pressing (ECAP) under a condition of various pressing temperatures. Pure Mg was susceptible to shear localization during ECAP; surface cracking occurred along to the direction of shear localization at lower temperatures than 573 K. Uniform flow occurred at 573 K, resulting in the successful 4 repetitive ECAP. The ECAP of Mg alloys containing Al (AZ series alloys) was unsuccessful at even higher temperature than 573 K. However, the ECAP temperature of AZ series alloys hot-rolled before ECAP became lowered, and the temperature for successful ECAP decreased with decreasing Al content. In particular, the hot-rolled AZ31 alloy could be ECAPed at 493 K. The ECAPed AZ31 alloy revealed the microstructure of dynamically recrystallized grains with a grain size in, range of 1 to 10 mum. The deformation during ECAP was analyzed by dislocation characteristics.