<p>A base film of a digital compact cassette tape comprising at least two layers consisting of laminated biaxially oriented polyester films, one surface of which has center line average roughness of 5 to 20 nm, and the other surface of which has center line average roughness of 15 to 45 nm, and which has a Young's modulus in a machine direction of at least 600 kg/mm<2>, which base film is excellent in running stability and electromagnetic conversion characteristics.</p>