To obtain a composition which can easily form a heat seal layer by extrusion and has excellent bondability to, especially, PP by incorporating a specified amount of an ethylene/α-olefin copolymer having a specified density with a specified amount of a tackifier.

This composition comprises 70-95 wt.% ethylene/α-olefin copolymer having a density of 0.880-0.910 g/cm3 and 5-30 wt.% tackifier (e.g. alicyclic hydrocarbon). The ethylene/α-olefin copolymer is desirably the one in which the number of carbon atoms of the α-olefin is 3-20, and MFR is 0.1-20 g/10 min as measured at 190°C under a load of 2,160 g and/or the one in which the ratio of the weight-average molecular weight to the number-average molecular weight is 3 or below as measured by GPC, and the relationship: Tm<-1.8×SCB+138 is held (wherein Tm(°C) is the temperature at which the maximum peak appears in a thermogram as determined by differential scanning calorimetry, and SCB is the number of short chains per 1,000 carbon atoms as determined by 13C-NMR spectroscopy).