The vehicle battery case structure includes a top plate and a bottom plate, a side plate provided around the bottom plate, a partition plate provided in a lattice shape on the top surface of the bottom plate to form a plurality of regions for accommodating the battery pack with the side plate, a slit portion into which the side plate and the partition plate can be inserted, and a fixing portion to which the top plate is fixed, and a fastening member bonded to the top surface of the bottom plate at the intersection of the side plate and the partition plate and at the intersection of the partition plates in a state in which at least one of the side plate and the partition plate is inserted into the slit portion.