PROBLEM TO BE SOLVED: To provide a method for coagulating seaweed Undaria pinnatifida Suringar by which a food comprising 100% of the seaweed Undaria pinnatifida Suringar can be produced without adding another food material and a method for producing noodles of the seaweed Undaria pinnatifida Suringar and a method for producing plates of the seaweed Undaria pinnatifida Suringar utilizing the method for coagulating the seaweed Undaria pinnatifida Suringar. SOLUTION: Water and a solvent are added to seaweed Undaria pinnatifida Suringar and the resultant mixture is heated to dissolve the seaweed Undaria pinnatifida Suringar. The prepared seaweed Undaria pinnatifida Suringar dissolved and converted into a pasty state is cooled to normal temperature, then extruded in a state of a desired shape into a coagulating solution by using an extrusion molding machine, dipped in the coagulating solution for a prescribed time and coagulated into the desired shape. After the coagulation, the resultant coagulated seaweed Undaria pinnatifida Suringar is taken out of the coagulating solution to remove the coagulating solution sticking to the surface of the coagulated seaweed Undaria pinnatifida Suringar.
