A semiconductor memory, including a plurality of word lines, a plurality of bit lines, a plurality of memory cells provided at intersections between the plurality of word lines and the plurality of bit lines, and a sense amplifier for reading out what is stored in the memory cells, the semiconductor memory including: bit line selection means for selecting a bit line from among the plurality of bit lines; switch means for turning ON/OFF a current of the bit line selected by the bit line selection means; current generation means for generating a threshold current; means for extracting a differential current between the selected bit line current and the threshold current when a value of the selected bit line current is greater than that of the threshold current; voltage conversion means for converting the differential current to a voltage; and determination means for determining a magnitude relationship between the threshold current and the selected bit line current based on an output voltage from the voltage conversion means.