Naturally formed frost on heat exchangers of low temperature devices is a cause for both increased resistance to air-passage and reduction of heat transfer. Therefore, defrosting operations will be needed when the frost has collected a lot because of the deterioration of efficiency of the heat exchanger. Focusing on the size of the droplets, the authors’ group artificially changed the characteristics of the cooling surface by machining shapes of 100 microns order on the cooling surface. By doing so, they have succeeded in producing zones with no frost-crystal growth on the surface. In this study, we investigated the effects of the groove patterns on the frosting phenomenon under natural convection condition varying the cooling surface temperature from -75℃ to -10℃.