There is provided a plastic base material having a reformed layer 2 formed on a plastic substrate 1 by reforming the surface layer thereof into a component containing fluorine at the ratio of the number of fluorine atoms to the number of carbon atoms, F/C, of 0.85 or more and 1.30 or less, and having highly durable water repellency and ink repellency. The method of manufacturing such a plastic base material comprises a step of reforming the surface of the plastic substrate 1 into a fluorine-containing carbon layer by imparting a specific energy to fluorine-containing plasma by applying an RF bias voltage to the plastic substrate 1 to form a surface having highly durable water repellency and ink repellency. A highly durable ink-jet printer that enables high-quality printing can be provided by the use of a head for an ink-jet printer fabricated by using this plastic base material.