A method of manufacturing a water repellent film includes, before a formation step of forming an organic film on a substrate using a silane coupling agent by a vapor phase deposition method under film formation conditions, a step of specifying the film formation conditions using a test substrate of a same material as the substrate used in the formation step. The film formation condition specifying step includes: specifying film formation temperature to be not lower than a temperature at which the silane coupling agent evaporates and to be lower than a temperature at which the silane coupling agent bumps; and forming an organic film of the silane coupling agent on the test substrate at the specified film formation temperature, measuring by optical microscopic observation a time at which a bead of surplus water repellent material is formed, and specifying the film formation duration to be shorter than the measured time.