A sheet-form electrode for a secondary battery includes a current collector, an electrode active material layer formed on one surface of the current collector, a porous polymer layer formed on the electrode active material layer, and a first porous supporting layer formed on the porous polymer layer. The sheet-form electrode can have supporting layers on at least one of the surfaces thereof to exhibit surprisingly improved flexibility and prevent the release of the electrode active material layer from a current collector even if intense external forces are applied to the electrode, thereby preventing the decrease of battery capacity and improving the cycle life characteristic of the battery.