A manufacturing method of a semiconductor memory device includes the steps of selectively forming a field oxide film (22) and a gate oxide film (21) on a semiconductor substrate (20), depositing a first conductive layer (23) on an entire surface of the resultant structure, selectively etching the first conductive layer (23) located in a region other than an element region, oxidation of the entire surface of the resultant structure, depositing a second conductive layer (27) on an entire surface of the resultant structure, and etching the first conductive layer (23), the oxide film (26), and the second conductive layer (27) using the same mask to form a plurality of floating gates by the first conductive layer (23) and to form a plurality of control gates by the second conductive layer (27), wherein the step of selectively etching the first conductive layer (23) includes the first etching step of forming cell slits (24) for separating the plurality of floating gates from each other and the second etching step of forming removed regions (25) each of which includes only one end of each of the plurality of control gates.