A storage device includes bit lines including a first bit line and a second bit line, memory units including a first memory string having memory cells connected in series, connected to the first bit line, and a second memory string having memory cells connected in series, connected to the second bit line, word lines each connected in common to a gate of a memory cell in the first string and a gate of a memory cell in the second string, and a controller configured to control voltages applied to the bit lines and the word lines during writing. When writing is performed on a selected memory cell of the first memory string, a first voltage is applied to a selected word line connected to the gate of the selected memory cell while a second voltage higher than a zero voltage is applied to the first bit line.