The present invention relates to an epoxy resin with improved water resistance and a composition comprising same and, more specifically, to: an epoxy resin which is prepared by the reaction of epihalohydrin and a diol component including anhydrosugar alcohol and a diol other than the anhydrosugar alcohol in a specific content ratio, thus exhibiting excellent eco-friendliness and improved water resistance, and, when applied to a coating composition, exhibits an anti-fog effect and at the same time can provide a coating with improved durability against moisture; and a composition comprising the epoxy resin (preferably, an anti-fog coating composition).