A soft thermoplastic resin composition comprising: 100 parts by weight of a resin component (A) containing 65 to 85 parts by weight of a vinyl chloride resin having a degree of polymerization of 2000 or less, and 15 to 35 parts by weight of a polyhydroxyalkanoate; 0.1 to 8 parts by weight of a resin component (B) which is one or more resins selected from the group consisting of a (meth)acrylate resin and an acrylonitrile-styrene resin, and has a weight average molecular weight, in terms of the polystyrene, of 400,000 or more; and 12 to 22 parts by weight of a plasticizer.