Battery mounting structure of frame vehicle

A battery mounting structure for a frame vehicle supports a battery pack by a pair of left and right side frames extending in a vehicle front-rear direction. The battery pack is divided into multiple battery packs arranged along the vehicle length, and each divided battery pack is connected to the side frames through a support member extending in a vehicle width direction. Each divided battery pack inclines independently according to torsion of the side frames, and suppresses twisting and reducing the likelihood of battery failure.