The present invention provides a coating composition capable of forming a fluorine-containing coating layer having a low refractive index and a high hardness, a coating layer formed by using the coating composition, an anti-reflecting layer using the coating layer and an anti-reflecting film and an image display device to which the anti-reflecting layer is applied. The coating composition according to the present invention comprises (A) a binder system containing a fluorine-containing component (a) having one or both of a functional group which can be cured by ionizing radiation and a polar group which can be heat-cured, and contains both an ionizing radiation-curable group and a heatcurable polar group as a whole and (B) an inorganic superfine particle of the order of submicron in size which can be dispersed in a colloidal state in a liquid medium for preparing a coating liquid. The coating layer formed using this coating composition is preferable for forming a light-transmitting layer, particularly, a low-refractive index layer 20, constituting a monolayer type or multilayer type anti-reflecting layer 17.