The invention relates to an electrode for a secondary battery, preparation thereof, and a secondary battery and a cable-type secondary battery comprising the same. The electrode for a secondary battery, comprising 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 for a secondary battery according to the present disclosure has supporting layers on at least one of 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.