A remarkable sea surface cooling (SSC) event was observed in the eastern sea of Korean peninsula based on new generation sea surface temperature (NGSST) satellite images in September 2005, when typhoon Nabi passed over the East Sea. The degree of SSC ranged from $1^{circ}C;to;4^{circ}C$, and its maximum was observed in the southeastern sea area. Daily variations in sea surface temperature at a longitudinal line $(35^{circ}-41^{circ}N,;132^{circ}E)$, derived from satellite data for September 1-13, 2005, showed that the SSC lasted about 3 days after the typhoon passed in the south of $39^{circ}N$, whereas it was unclear in the north of$39^{circ}N$. Water temperature measured by a mooring buoy suggested that the SSC was caused mainly by a vertical mixing of the water column driven by the typhoon, rather than by coastal upwelling.