A boot for an automobile comprises two terminal annular parts and a barrel part intervening between the two terminal annular parts. This boot is obtained by injection molding a flexible PVC material. The flexible PVC material of one type (I) is composed of a polymer component and a plasticizer, which polymer component is obtained by blending high polymerization degree and low polymerization degree PVC's respectively having an average polymerization degree in specific ranges, with the mixing ratio of the two PVC's being in a specific range. The flexible PVC material of the other type (II) is composed of a polymer component and a plasticizer, which polymer component is obtained by blending a cross-linked resin having a non-gel component average polymerization degree and a cross-linking degree in respectively specific ranges with a non-cross-linked resin having an average polymerization degree in a specific range, with the mixing ratio of the two PVC's in a fixed range. The boot formed of the material of Group I or II incurs no layer separation even after a heat resisting test and induces no bleeding even after a light resisting test. The boot formed of the material of Group II acquires delustered appearance even when the metal die has not been treated by honing in advance.