A semiconductor memory device includes: a gate electrode formed on a semiconductor layer via a gate insulating film; a channel region disposed under the gate electrode; diffusion regions disposed on both sides of the channel region and having a conductive type opposite to that of the channel region; and memory functional units formed on both sides of the gate electrode and having the function of retaining charges, wherein each of the diffusion regions has: a high-concentration impurity region disposed so as to be offset from the gate electrode; and a low-concentration impurity region disposed in contact with the high-concentration impurity region so as to overlap with the gate electrode, and an amount of current flowing from one of the diffusion regions to the other diffusion region is changed when a voltage is applied to the gate electrode in accordance with an amount of charges retained in the memory functional units.