PURPOSE: To provide an ink composition for an overhead projector sheet made of opaque or translucent plastic film, which contains a mixed solvent consisting of an aromatic hydrocarbon solvent and an aromatic ketone solvent and produces clear images.

CONSTITUTION: The ink composition is used for an overhead projector sheet (PS sheet) prepared by coating an opaque or translucent plastic film with a dispersion of synthetic resin which consists mainly of a mixed solvent of an aromatic hydrocarbon solvent and an aromatic ketone solvent. The composition is obtained by adding an aromatic ketone solvent to a conventional PS sheet ink composition, thus forming said mixed solvent. The composition may contain common additives for oil ink for felt pen, such as perfume, preservative, corrosion inhibitor, antioxidant and surfactant.