A method for forming a plurality of stripe-like phosphor layers on a surface of a substrate constituting a plasma display panel, the surface having a plurality of parallel ribs disposed thereon and grooves defined between two adjacent ribs, includes the steps of: molding a phosphor paste composed of a phosphor substance and a first synthetic resin into filament-like article; placing the molded filament-like article into each groove; filling the grooves with a solvent optionally containing a second synthetic resin compatible with the first synthetic resin; and conducting a sintering treatment of the substrate to form the phosphor layers in the grooves. An apparatus for forming a plurality of stripe-like phosphor layers on a surface of a substrate having a plurality of parallel ribs disposed thereon and grooves defined between two adjacent ribs, includes: a mounting base for mounting the substrate thereon and a supplier for supplying a filament-like article into the grooves, the filament-like article being made of a phosphor substance and a synthetic resin.