PROBLEM TO BE SOLVED: To provide an antifogging composition capable of forming an antifogging layer which has excellent long sustainability of antifogging properties and antifogging performance, and transparency, suppresses falling off of colloidal silica even under high humidity environment, and is excellent in water resistance.SOLUTION: An antifogging composition contains at least two kinds of colloidal silica having different average primary particle sizes, where a ratio (D2/D1) of an average particle size (D1) of colloidal silica having the smallest average primary particle size to an average primary particle size (D2) of colloidal silica having the largest average primary particle size is 2 to 15.SELECTED DRAWING: None【課題】防曇性及び防曇性能の長期持続性、並びに透明性に優れ、且つ、高湿環境下でもコロイダルシリカの脱落が抑制され、耐水性に優れる防曇層を形成することができる防曇性組成物を提供する。【解決手段】 平均一次粒子径が異なる少なくとも２種のコロイダルシリカを含有し、平均一次粒子径が最も小さいコロイダルシリカの平均一次粒子径（Ｄ１）と、平均一次粒子径が最も大きいコロイダルシリカの平均一次粒子径（Ｄ２）との比（Ｄ２／Ｄ１）が２～１５であることを特徴とする防曇性組成物。【選択図】なし
