A method of manufacturing a semiconductor storage device according to an embodiment includes: stacking a first wiring layer; stacking a memory cell layer on the first wiring layer; and stacking a stopper film on the memory cell layer. The method of manufacturing a semiconductor storage device also includes: etching the stopper film, the memory cell layer, and the first wiring layer; polishing an interlayer insulating film to the stopper film after burying the stopper film, the memory cell layer, and the first wiring layer with the interlayer insulating film; performing a nitridation process to the stopper film and the interlayer insulating film to form an adjustment film and a block film on surfaces of the stopper film and the interlayer insulating film, respectively; and forming a second wiring layer on the adjustment film, the second wiring layer being electrically connected to the adjustment film.