There are disclosed an electrode for electrolysis capable of efficiently forming ozone by electrolysis of an electrolytic solution (e.g., water) at ordinary temperature with a low current density, and an electrolysis unit using the electrode. The electrode for electrolysis includes a substrate and a surface layer formed on the surface of the substrate, and the surface layer is made of an amorphous insulator, for example, a thin film of amorphous tantalum oxide, amorphous tungsten oxide or amorphous aluminum oxide.