The invention provides a surface-treated calcium carbonate that when incorporated into a paste resin, can impart low viscosity and high thixotropy and offers excellent storage stability, and paste resin compositions containing the same. The surface-treated calcium carbonate is a calcium carbonate surface-treated with a surface treatment agent containing a sodium salt or potassium salt of a fatty acid, wherein the total content of a sodium salt and a potassium salt of lauric acid, a sodium salt and a potassium salt of palmitic acid and a sodium salt and a potassium salt of stearic acid in the surface treatment agent is 80% by weight or more, the content of the sodium salt and potassium salt of lauric acid is within the range of 30% to 60% by weight, the content of a sodium salt and a potassium salt of an unsaturated fatty acid in the surface treatment agent is 5% by weight or less, and the BET specific surface area is 10 m2/g or more.