A displacement prevention coating agent is provided which can prevent a displacement in lens processing, which is soluble in water and which exhibits a transparent appearance at least after being cured. The displacement prevention coating agent may coat the front and rear surfaces of a lens so that when cutting processing is performed on an end surface of the lens, a holding position of the front and rear surfaces of the lens held by a chuck device is prevented from being displaced. A water-repellent coat layer may be formed as a membrane such that the end surface has a shape corresponding to a frame. The displacement prevention coating agent may be formed of an aqueous solution whose main components are a hydrophilic resin, a surfactant having a perfluoro group and an emulsion.