Abstract: The present invention discloses an input buffer which can improve the properties of a setup time and a hold time of an input signal. When the setup time is important, a path of a short delay time is employed, and when the hold time is important, a path of a long delay time is used. Therefore, the internal setup time/hold time may be suitably selected in the system application conditions. For this, the input buffer includes: a buffer for receiving a signal through an input pin; a plurality of delay units for delaying the signal inputted from the buffer by a different delay time; and a selecting unit for selectively outputting one of the output signals from the plurality of delay units according to an externally-inputted reference signal and the logic variation of the input signal from the buffer.