Automobile rear body structure

Disclosed is an automobile rear body structure capable of allowing a space created between a rear bumper reinforcing member and a line connecting respective rear ends of a pair of rear side frames to be effectively utilized. In this automobile rear body structure, a rear end cross member 30 has an expanded portion 31a formed to expand rearward relative to respective rear ends 10a of a pairs of rear side frames 10, and a rear floor pan 20 has a rear edge including a protruded portion 21. The protruded portion 21 is formed to protrude relative to the rear ends 10a of the pairs of rear side frames 10 toward the expanded portion of the rear end cross member 30 and connected to the rear end cross member 30, so as to allow a luggage compartment space to be enlarged rearward relative to the rear ends 10a of the pairs of rear side frames 10.