In a control method of a washing machine, a primary nephelometric turbidity unit (NTU) of washing water is sensed (S160) before a washing course is started in a washing cycle, a second NTU is sensed (S160) based on the primary NTU (N1), and a washing time, an amount of washing agent, and/or a number of times (S200, S210, S220) of rinsing are varied based on a difference value between the primary NTU (N1) and the secondary NTU, thereby improving washing performance and washing efficiency.
