The present invention discloses an automatic precharge apparatus of a semiconductor memory device. An object of the present invention is to perform a sable precharge operation unrelated to change of the clock frequency by controlling to perform an precharge operation after constant delay time, regardless of an external clock signal. The automatic precharge apparatus of a semiconductor memory device comprises an automatic precharge signal generating unit receiving external control signals and then generating an internal precharge command signal, and outputting an automatic precharge signal by using the internal precharge command signal and control signals being related to a bust operation, a ras precharge signal generating unit for generating a ras precharge signal by receiving the automatic precharge signal, a delay unit for outputting a write recovery signal with a constant delay time, which is disabled in the reading operation and only enabled in the writing operation, when an internal precharge command signal is inputted, a ras generating unit for generating a ras signal without a delay time when inputting an external precharge command signal, whereas after a constant delay time in response to the write recovery signal when inputting the ras precharge signal.