A composition for a platelet storage container that enables continuous and stable long-term storage of high number of platelets has a composition of: (a) 30-40% by weight of a hydrogenated block copolymer comprising a polymer block A composed mainly of a vinyl aromatic compound and a polymer block B composed mainly of a conjugated diene； (b) 35-65% by weight of polyethene having a density of 0.860-0.900 g/cm3, the polyethylene being obtained by copolymerizing ethylene and an ±-olefin； and (c) 5-25% by weight of poly(methylpentene), or of a (co)polymer composed mainly of methylpentene with ethylene or an ±-olefin, component (c) having an MFR of 3-20 g/10 min, a density of 800-900 g/cm3, and a melting point (Tm) of 180°C or lower as measured by differential scanning calorimetry (DSC).
