To provide a stable coating state free from the occurrence of coating unevenness in a field requiring the coating of a thin film such as an optical film with high precision.

In the method of applying a coating liquid to form a coating layer having ≤5 μm film thickness when coating on a supporting body by applying the coating liquid on the back surface of the travelling belt like flexible supporting body 16 by a gravure coating apparatus 10, a pre-coater 15 is provided in the upstream side in the travelling direction of the supporting body with respect to the gravure coating apparatus and the coating liquid is applied on the supporting body to have a film thickness 50-500% of a designed thickness (the said film thickness when coating) by the pre-coater.