A method of manufacturing a semiconductor storage device according to an embodiment of the present invention includes forming dummy cells 611, to 618 at a position adjacent to a reference cell 412, and implanting an impurity into the dummy cells 611, to 618 using a mask that covers the reference cell 412. Here, the process of implanting the impurity is carried out so that the impurity exudes out of the dummy cells 611, to 618 to the reference cell 412.