A page buffer includes a bit line controller connected between a bit line and a sensing node, wherein the bit line controller is capable of adjusting a potential level of the sensing node, based on a cell current amount of the bit line, by performing an evaluation operation. The page buffer also includes a first latch unit connected to the sensing node, wherein the first latch unit is capable of adjusting an operation period of the evaluation operation. The page buffer further includes a second latch unit for latching verify data, based on the potential level of the sensing node.