This thiol group-containing polymer is represented by the general formula HS-(R-Sr)n-R-SH (R is an organic group and/or branch alkylene group comprising a -O-CH2-O- bond; n is an integer 1 to 200; r is an integer 1 to 5; and the mean value of r is 1.1 to 1.8). A curable composition in which this thiol group-containing polymer is used can be used in sealants, adhesives, paints, and the like where the properties of low specific gravity, low viscosity, and low glass transition temperature are required. This curable composition has improved resilience and weather resistance and can therefore be used in sealants, adhesives, paints, and the like where resilience and weather resistance are required.