PURPOSE: To restrain a pillar at a rear edge of a door opening part from being deformed by impact force at the time of a rear-end collision so as to prevent a sliding door from becoming hard to open at the time of the rear-end collision.

CONSTITUTION: A sliding door is provided slidably along a guide rail on an outer surface of a body side wall. A quarter panel 12 has front side and rear side pillar parts 12a, 12b; an upper side connecting part 12c, an intermediate connecting part 12d and a lower side connecting part for connecting upper end parts, intermediate parts and lower end parts of both pillar parts respectively to each other; and a guide rail supporting part 12f extended to the rear fender side from a part between the intermediate connecting part and lower side connecting part of the rear side pillar part so as to support a guide rail rear end fixing part of the rear fender. Fragile parts 21, 24 such as cutout parts or holes are formed at a guide rail supporting part of an inner panel and the pillar at the rear end of a body, and rigidity of the fragile parts to rear load acting at the time of a rear-end collision is made lower than that of a pillar at the rear edge of a door opening part.