To protect a battery pack at the time of a rear-end collision of an electric car including the battery pack arranged between rear side members arranged in a rear part of the car.

In a battery pack mounting structure for electric cars, a pair of rear side members having a front portion, a rear portion, and a rising portion are arranged at both lateral sides, intermediate portions of the rear side members are coupled to each other with a cross member, and a battery pack is mounted on a vehicle body by a sub-frame to be coupled to the rear side members and the cross member. The cross member is arranged at a position lower than a bent portion that connects the rising portion and the rear portion of each of rear side members. The sub-frame includes a ring-like support frame that extends in a horizontal direction and surrounds an outer periphery of the battery pack. A front side portion and both lateral side portions of the support frame are coupled to the cross member and the rear portions of the rear side members, respectively, by coupling portions.