Disclosed is a method of manufacturing pulp and paper using Rhodophyta, including immersing Rhodophyta in an extraction solvent able to dissolve agar gel for a predetermined time period to dissolve the agar gel in the extraction solvent, reacting the dissolved agar gel with a reaction solvent to be converted into a fiber, curing the fiber using a curing agent, and pulping the cured fiber. The method of the current invention is advantageous because of lower manufacturing costs, due to eliminating the need to purchase wood. Further, the use of chemicals for lignin removal and bleaching drastically decreases, thus preventing environmental contamination. Furthermore, since a final product does not contain harmful chemicals, humans and the environment are not negatively affected.