The invention provides a semiconductor memory device which realizes high speed reading by automatically adjusting and optimizing charge and discharge timings even when a change in an operation environment such as a variation in an operation voltage, an operation temperature, a process parameter and so on occurs. First and second dummy bit lines are provided for a bit line, each having a wiring load twice the wiring load of the bit line. A first sense circuit sensing the voltage of the first dummy bit line is provided to control a charging time according to a first sense signal. A second sense circuit sensing the voltage of the second dummy bit line is further provided to control a discharging time according to a second sense signal. A sense amplifier sensing the voltage of the bit line is activated in response to the second sense signal.