A rinse water heating device for a dish washer includes a water tank for storing a rinse water used for washing dishes, a rinse water tank divided from the water tank by a separation plate positioned at a lower portion of the water tank, partitions installed in the rinse water tank to form a rinse water guide path in a zigzag pattern, a heater installed along the rinse water guide path, and an inlet pipe installed to introduce water in the water tank into the rinse water tank. The water tank and the rinse water tank are divided from each other, so this device may subsequently heat a small amount of water in the rinse water tank within a short time. Therefore, the rinse water heating device allows an automatic dish washer to wash dishes with enhanced sterilizing, cleaning and drying abilities, thereby ensuring effective rinsing and washing.