A mounting structure for a power storage device includes: a power storage device including a power storage stack and a housing case; a floor member; and a rear bracket. The housing case includes a lower case having a rear wall, and an upper case. The floor member is provided with an attachment portion for attaching the rear bracket. The rear bracket includes a front end portion and a rear end portion that is attached to the attachment portion. The power storage stack is disposed inside the housing case to provide a gap between the power storage stack and the rear wall. The front end portion of the rear bracket is fixed to the rear wall to be located between an upper surface and a lower surface of the power storage stack in an up-down direction.