An electricity storage unit of the present disclosure includes: an electricity storage device; a holder for holding this electricity storage device; a case having a tubular side wall part and a bottom surface part closing one end of the side wall part, the case being formed with an opening at another end of the side wall part; and a cover for covering the opening. The electricity storage device and the holder are housed inside the case. At least a part of the cover is inserted inside the case. An aperture is formed at least part of a region between an outer periphery of the cover and an inner surface of the side wall part.