A base film for dicing sheets, the base film being for use in a dicing sheet comprising the base film and a pressure sensitive adhesive layer laminated on one surface of the base film, wherein the base film comprises at least a first resin layer that is suitable for being in contact with the pressure sensitive adhesive layer of the dicing sheet and a second resin layer that comes into contact with the first resin layer when the base film for dicing sheets is wound up, the first resin layer has a thickness of 10 to 120 μm, the first resin layer comprises: (i) a resin composition that contains an ethylene-based copolymer selected from an ethylene/α,β-unsaturated carboxylic acid copolymer and an ethylene/α,β-unsaturated carboxylic acid/α,β-unsaturated carboxylic ester copolymer, a ternary copolymer having a constitutional unit originated from α-olefin, a constitutional unit originated from glycidyl (meth) acrylate or glycidyl unsaturated ether and a constitutional unit originated from vinyl ester or unsaturated carboxylic ester, and a polyolefin, or (ii) a resin composition that contains an ethylene/(meth)acrylic acid copolymer and a polypropylene-based resin, the second resin layer has a crystallinity of 28% to 45%, the second resin layer contains an olefin-based resin, a ratio of a tensile elastic modulus of the first resin layer to a tensile elastic modulus of the second resin layer is 1.2 to 3.0, and a ratio of a thickness of the first resin layer to a thickness of the base film for dicing sheets is 25% to 80%, wherein the crystallinity of is determined by extrusion molding of the raw material of the resin layer using a compact T-die extruder to form a single resin film layer having a thickness of 100 μm, heating the resin film layer at a heating rate of 20°C/min from the ordinary temperature to 250°C and holding it at 250°C for 10 minutes; cooling the resin film layer at a cooling rate of 20°C/min to -60°C, and holding it at -60°C for 10 minutes, and thereafter heating it again at a heating rate of 20°C/min to 250°C to obtain a DSC curve whose endothermic peak area is measured using a differential scanning calorimeter, from which the melting heat quantity (W/g) is obtained; crystallinity is calculated from the obtained melting heat quantity (W/g) using the equation: crystallinity (%)=(melting heat quantity/293)×100; and wherein the tensile elastic modulus of each of the first resin layer and the second resin layer are obtained by extrusion molding of the raw materials for extrusion of the first resin layer and second resin layer using a compact T-die extruder to produce single-layer resin films having a thickness of 100 μm; cutting each film into a test specimen of 15 mm (MD direction)×140 mm (CD direction); and measuring the tensile elastic modulus at 23°C in accordance with JIS K7161: 1994 and JIS K7127: 1999 using a tensile tester (Autograph AG-IS 500N) at a rate of 200 mm/min with a distance between the chucks of 100 mm. (i) a resin composition that contains an ethylene-based copolymer selected from an ethylene/α,β-unsaturated carboxylic acid copolymer and an ethylene/α,β-unsaturated carboxylic acid/α,β-unsaturated carboxylic ester copolymer, a ternary copolymer having a constitutional unit originated from α-olefin, a constitutional unit originated from glycidyl (meth) acrylate or glycidyl unsaturated ether and a constitutional unit originated from vinyl ester or unsaturated carboxylic ester, and a polyolefin, or (ii) a resin composition that contains an ethylene/(meth)acrylic acid copolymer and a polypropylene-based resin,