The invention relates to a power saving method in a sleep mode and a keyboard controller using the same. The method is adapted for a triangular-type scan keyboard controller including a plurality of input/output (I/O) pins. The method includes the steps of: providing a first clock source and a second clock source, wherein the frequency of the second clock source is much lower than the frequency of the first clock source. In a normal mode, a scan pulse is sequentially outputted from the I/O pins according to the frequency of the first clock source. In a sleep mode, the scan pulse is sequentially outputted from the I/O pins according to the frequency of the second clock source. When a specific one of the I/O pins outputs the scan pulse, the other I/O pins are used for detecting.