Abstract. Multi-scale evaluations of submarine groundwater discharge (SGD) have been made in Saijo, Ehime Prefecture, Shikoku Island, Japan, by using seepage meters for point scale, ²²²Rn tracer for point and coastal scales, and a numerical groundwater model (SEAWAT) for coastal and basin scales. Daily basis temporal changes in SGD are evaluated by continuous seepage meter and ²²²Rn mooring measurements, and depend on sea level changes. Spatial evaluations of SGD were also made by ²²²Rn along the coast in July 2010 and November 2011. The area with larger ²²²Rn concentration during both seasons agreed well with the area with larger SGD calculated by 3D groundwater numerical simulations.