The purpose of the invention is to provide a structure for mounting an electric power storage device, which can prevent shaking of the electric power storage device. The structure for mounting an electric power storage device includes: the electric power storage device (10) that outputs the energy used in running a vehicle, a vehicle body that is provided with a recess (121) for storing the electric power storage device, fastening members (31) that fix the electric power storage device to the recess, and reinforcements (41). The reinforcements (41) are disposed at locations that enclose the recess and the electric power storage device, and are fixed to the vehicle body. The reinforcements (41) press the electric power storage device against the recess (121).