A semiconductor storage device of an embodiment includes: a laminated body including electrode layers and insulating layers alternately stacked in a first direction; a semiconductor layer disposed in the laminated body; a first insulating film disposed between the laminated body and the semiconductor layer; a charge storage film disposed between the laminated body and the first insulating film, thicknesses of the charge storage film in a second direction crossing the first direction in the regions corresponding to the electrode layers being different from that in the regions corresponding to the insulating layers, the charge storage film comprising: a second insulating film disposed between the laminated body and the first insulating film, and a third insulating film disposed between the second insulating film and the regions corresponding to the electrode layers, the third insulating film having a density different from that of the second insulating film.