PROBLEM TO BE SOLVED: To provide a coating antifogging agent which has excellent storage stability, excellent coatability, can uniformly be coated on substrate films, and can further form antifogging layers having excellent initial antifogging property, antifogging durability, antifogging dripping property, transparency and coating film uniformity. SOLUTION: This coating antifogging agent is characterized by comprising 100 pts.wt. of an aqueous medium, 0.1 to 20 pts.wt. (as solid content) of colloidal silica in which 0.010 to 0.050 &mu；m of particles are linked to each other in a length of 0.050 to 5.0 &mu；m, 0.1 to 10 pts.wt. (as solid content) of colloidal alumina, and 0.1 to 10 pts.wt. of a water-soluble resin having a weight-average mol.wt. of 100,000 to 4,000,000, wherein the weight ratio of the total amount of the solid contents of the colloidal alumina and the colloidal silica to the amount of the water-soluble resin is 100:1 to 100:50.
