There are various kinds of cereals used in sunsik manufacturing. Different harmful microorganisms that can contaminate these cereals have been reported. According to the different sizes of cereals used, black bean, black rice, and millet were artificially contaminated with Escherichia $Coli.$ $E.$ $coli$ contamination in cereal samples was detected after different washing steps under different conditions. The increase of washing time did not have any effect with regard to reducing $E.$ $coli$ in samples. Among several ratios between the washing solution and sample, 2:1 that have little influence to reduce $E.$ $coli$ contamination have been determined. The temperature of the washing solution is an influencing factor as well. Washing with solution at $40^{circ}C$ could reduce 1 log of $E.$ $coli$ in samples. Among different concentrations of saline used as a washing solution, 5% could reduce 2~3 log $E.$ $coli$ in contaminated samples. However, the saline adds a salty taste to cereals when used during the washing step. To remove that, an extra washing step and large amount of washing solution are necessary in sunsik manufacturing.