PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing a resin base material with a coating film, without causing a poor appearance by a liquid reservoir of a coating liquid.SOLUTION: The manufacturing method comprises a coating process of coating the coating liquid being 10-200 mPa.s in viscosity at 23°C on the resin base material 10A by a wet coat method. The resin base material 10A comprises one or more of corner parts 13a, 13b, 13c and 13d, and a guiding projection 20A in which the coating liquid coated in the coating process flows down by going along a surface, is formed in at least one among these. After the coating process, the resin base material 10A is arranged so that the corner part 13a(O)forming the guiding projection 20A is positioned below, and a part of the coating liquid is made to flow down by going along the guiding projection 20A (a leveling process). After the leveling process, the guiding projection 20A is removed from the resin base material 10A (a projection removing p
