A power storage device is a power storage device provided on a lower surface of a floor panel of a vehicle, the power storage device including: a housing case; a power storage module housed in the housing case; and a cooler housed in the housing case to cool the power storage module, wherein the housing case includes a bottom plate, a refrigerant passage through which a refrigerant flows is formed in a portion of the housing case, the portion being located above the bottom plate, and the refrigerant passage is connected to the cooler.