In the non-volatile semiconductor memory device having a sense amplifier for sensing data stored in a selected memory cell by comparing cell current differences from a reference cell, a current sink unit coupled in parallel with a reference line and a data line are provided. The reference line connects between the reference cell and the sense amplifier, and the data line connects between the selected memory cell and the sense amplifier, where the current sink unit together increases currents of the reference line and the data line. Also, the device includes a sink current control unit having a configuration of a current mirror with the current sink unit, the sink current control unit consisting of a switching unit and being for controlling a sink current of the current sink unit. The device improves data sensing speed and controls sensing current in conformity with the characteristics of a memory cell.