Hot steel can be cut more easily than the cold steel. Experimental results of cutting hot steel with an abrasive water jet (AWJ) at temperatures > 1000°C have not been reported. Here, basic laboratory experiments with the AWJ showed the cutting phenomena using a small work piece of hot steel compared with cold steel. The experimental results showed that the relationship between cutting speed and thickness of hot steel was unexpectedly almost the same as for cold steel. According to the thermocouple measurement, the center temperature of the steel was maintained above 800°C. However, as estimated by heat transfer analysis, the surface temperature of the hot steel decreased to < 300°C. Therefore, when the hot steel was cut with the AWJ, the cut surface on which the abrasive acts became cold steel.