Background of the Study: Diarrhea is the raising of feces mass, the frequency of defecating, or the level of feces dilution. One of the factors that causes diarrhea is the microorganism which is spread through mouth by hand. The prevention of diarrhea can be done by hand-washing. Hand-washing is a disposal process of dirt and dust mechanically rinsed with clean water. Objective: to know the effect of health education about hand-washing towards mother’s knowledge level in preventing diarrhea on toddler and also to find out about the more effective way between lecturing and leaflet in presenting health education which increases mother’s knowledge level in preventing diarrhea on toddler. Research Method: Method of this research is Quasy-Experiment. There are 2 groups, i.e. treatment group (using lecturing) and control group (using leaflet). The population of each group is 42 and the sample in each group includes 30 respondents counted with Slovin formula. The sampling used in this research is Simple Random Sampling. The research has been conducted in July 2016. The data is collected using questionnaire. The statistic test uses wilcoxon and mann-whitney with significant rate <0,05. The findings: the result shows that there is an effect of hand-washing education towards knowleddge level by wilcoxon statistic test on control group and treatment group p=0,000(p<0,05). There is a significant effect on the knowledge level of treatment group and control group after being given health education with pretest p=0,007 (p<0,05) and postest p=0,000 (p<0,05). In health education methods, there is no significant effect in increasing the knowledge level either using lecturing or leaflet p=0,642 (p>0,05). Conclusion: The mothers who get health education about hand-washing will increase their knowledge in preventing diarrhea on toddler.