A battery installation structure is configured to control a behavior of a battery when a vehicle collides, so that a front side frame is ensured to be provided with a sufficient stroke for collision. The battery installation structure is suitable for allowing a battery to be installed on a front side frame of a vehicle body. The battery installation structure includes an installation base disposed on the front side frame, a battery base, and a rear support leg. The battery base is disposed on the installation base to support the battery. The rear support leg is disposed at a rear end of the battery base. A center of the battery base is fixed to a fixing portion of the installation base, a lower end of the rear support leg is fixed to a rigid member of the vehicle body, and the lower end of the rear support leg is formed with a fragile portion.