Disclosed is a crystalline metal oxide having a positive charge-induced region and a negative charge-induced region, which has a surface which has protrusions and recesses or a porous surface. The metal which configures the metal oxide is preferably an elemental metal or an elemental metal-containing alloy such as titanium, zirconium, titanium alloy, zirconium alloy or cobalt chromium alloy. The metal oxide is preferably one obtained by an anodic oxidation treatment of the metal which configures the metal oxide and the metal oxide can be suitably used as a biocompatible material or a member constituting a biocompatible material.
