Water apple is a local variety from Demak which has been SOP (standard operational procedures) related to water apple cultivation since 2010. The function of the water apple SOP is as a reference for GAP (Good Agriculture Practices) of water apple farming. The purpose of this study was to determine the level of application GAP and find out the factors related to the level of application GAP. We took three villages of water apple production centres as research location during 2018. Data collection was conducted through interviews with 72 randomly selected farmers. The level application of water apple GAP was analysed by the Likert Scale Scoring method, while the factors associated with the application of GAP were analysed by the Spearman Rank Correlation method. The results show that the application level of GAP on water apple farming is in medium category. Factors in the number of plants, land area, availability of capital, income, and input costs were positively related to the application level of GAP on water apple farming. Assistance to increase knowledge and skills is needed to increase the application of GAP so that the results of water apple farming will be better.