Variations of surface hardness of alumina induced by ion implantation were studied by using a dynamic ultramicrohardness tester changing the maximum loads as 2, 20 and 120 gf. Implanted ion species and energies were 0.4 MeV B⁺, 0.7 MeV Si⁺ in which 1.3 MeV Cu⁺, and their projection ranges were almost the same of 0.6μm. and 3 MeV of B²⁺, Si²⁺ and Cu²⁺. The implantation dose was mainly 1×10¹⁶ ions/cm². Hardness for the loads of 2 and 20 gf was increased in any implantation. But the change in hardness for 120 gf was negligibly small. Apparent depth profile of the dynamic hardness, which was obtained from the "load-depth" data in indentation, showed clear increase of hardness in the top layer and relatively softer layer beneath of it. The thickness of the harder layer was in-creased with the increase of the implantation energy. Heat treatment (1000°C. 1 hr, in Ar) made the surface softer generally. Comparing with the unimplanted samples. however, the dynamic hardness, especially for the loads of 20 gf was increased. There was a tendency that the heavier ion species and the higher energy implantation showed the larger increase of hardness.