The present invention relates to a method for manufacturing lithium hydroxide and lithium carbonate, and a device therefor. The present invention provides a method for manufacturing lithium hydroxide, comprising: a step of dissolving lithium phosphate in an acid; a step of preparing a monovalent ion selective-type electrodialysis device disposed in the order of a cathode cell containing a cathode separator, a monovalent anion selective-type dialysis membrane for selectively permeating a monovalent anion, a monovalent cation selective-type dialysis membrane for selectively permeating a monovalent cation, and an anode cell containing an anode separator, injecting the lithium phosphate dissolved in the acid between the anode separator of the anode cell and the monovalent cation selective-type dialysis membrane, and between the cathode separator of the cathode cell and the monovalent anion selective-type dialysis membrane, respectively, and injecting water between the monovalent cation selective-type dialysis membrane and the monovalent anion selective-type dialysis membrane; a step of obtaining an aqueous lithium chloride solution, and at the same time, obtaining a phosphoric acid aqueous solution formed as a byproduct, by applying an electric current to the monovalent ion selective-type electrodialysis device; and a step of converting the obtained aqueous lithium chloride solution into an aqueous lithium hydroxide solution.