A semiconductor memory device includes a memory block, and control logic. The memory block includes a plurality of memory cells. The control logic controls a peripheral circuit to perform a read operation on selected memory cells among the plurality of memory cells. The read operation includes a bit line precharge operation, an evaluation operation, and a sensing operation. The control logic is configured to control the peripheral circuit to float a common source line coupled to the memory block during at least a partial period of a period of the bit line precharge operation, in which a voltage of a plurality of bit lines coupled to the memory block increases.