The effects on udon noodles of adding 3%, 5%, 8% and 13% of Ulva pertusa powder were measured. The chlorophyll and magnesium contents increased with increasing addition of Ulva powder. Adding Ulva powder to the noodles also resulted in an increased vitamin C content and improved antioxidative activity. Scanning electron microscopy showed that adding Ulva powder resulted in a ruptured gluten network structure with many small holes. A sensory evaluation of the noodles with 8% Ulva powder addition showed a green color with a mushy texture, while 3 to 5% addition gave noodles with a firm texture and good taste. It is considered that the nutritional intake can be enhanced by regular consumption of Ulva noodles.