Abstract: A substrate of the surface protective film giving a film attached to the surface of a building material, a painted steel sheet, etc. for the purpose of prevention of damage easy applicability and easy removability and a surface protective film using the same, that is, a substrate of the surface protective film comprised of at least two film layers with different physical properties, wherein an outermost film layer forming an outermost surface corresponding to another surface facing one surface of the substrate exhibits a tensile modulus of elasticity based on JIS-K-7127 (2000) lower than a tensile modulus of elasticity of the substrate as a whole and a surface protective film comprised of such a substrate of the surface protective film on one surface of which an adhesive layer is formed.