The first high-resolution simulation of an observed polar low using a non-hydrostatic mesoscale numerical model with 2-km horizontal resolution is reported. The case studied is a remarkable polar low that developed over the Japan Sea on 21 January 1997. The simulation successfully reproduced the observed features of the polar low such as its horizontal scale, movement, spiral bands, a cloud-free eye, and cloud streets associated with the cold air outbreak. Detailed three-dimensional structures of the simulated polar low, which are difficult to observe by in situ measurement, have been clarified and its development mechanism is discussed.