A bitline sense amplifier including: an amplifier which is connected between a first sensing bitline and a second sensing bitline, and detects and amplifies a voltage difference between a first bitline and a second bitline in response to a first control signal and a second control signal; and an equalizer which is connected between a first supply line through which the first control signal is supplied and a second supply line through which the second control signal is supplied, and pre-charges the first bitline and the second bitline with a precharge voltage in response to an equalizing control signal, wherein the equalizer includes an equalizing enable transistor in which a source terminal is connected to the first supply line and performs equalizing in response to the equalizing control signal.