Antifogging agent

An antifogging agent, wherein, when a water film is formed on a principal surface of a base material treated with the antifogging agent, the water film has a water film uniformity index WE represented by the following formula (a) of 65% or more:

• WE
• =
• (
• S
• /
• TS
• )
• ×
• 100
• (
• a
• )
• wherein, in the formula (a), TS indicates a sum of frequencies in an area distribution indicating an area of a black region and a frequency thereof generated from an image for evaluation having a size of 1824×1824 pixels obtained by capturing an image of an object having a checkered pattern composed of black squares and white squares having a side length of 0.5 mm through the base material on which the water film is formed, S indicates a sum of frequencies included in a predetermined area range in the area distribution, and the predetermined area range indicates an area range in which a frequency is 5% or more of a total frequency in an area distribution indicating an area of a black region and a frequency thereof generated from a reference image having a size of 1824×1824 pixels obtained by capturing an image of the object through the base material, provided that a distance between the object and the base material is 2.5 cm, and a position of a digital camera for photographing the object is set such that 4900 black squares and white squares are included in an image having a size of 1824×1824 pixels.