a method of cleaning a washing tub mounted in a water tub of a washing machine includes supplying water necessary to clean the washing tub to the water tub , and rotating the washing tub while supplying heat to the water tub by means of at least one heat supply device mounted in the washing machine . the washing tub is maintained at high temperature when the washing tub is cleaned , whereby decontamination and disinfection efficiency is improved . also , water required to clean the washing tube is separately supplied to increase the rotating speed of a washing motor , whereby cleaning efficiency is improved .