PURPOSE: To provide a polyester film useful as a base film of a magnetic recording medium, which is excellent in chipping and scratch resistances and does not injure a well-surface-finished metallic guide, an insufficiently surface-finished metallic guide and a plastic guide.

CONSTITUTION: The title film contains 0.05-1wt.%, based on the polyester, inert particles (A) having a specific surface area of 50-150m2/g and a mean particle diameter of 0.05-0.3μm 3-30wt.%, based on component A, alumina having a mean particle diameter of 0.1-0.3μm and 0.005-5wt.%, based on the polyester, inert particles ' having a mean particle diameter of 0.3-1.2μm.