The Adriatic Sea is oligotrophic sea with the indented coastline. It is considered as one of the cleanest sea of Europe. However, in the summer, due to the large number of tourists, it is necessary to control the quality of sea water to determine is there any contamination, waste water, feces or microorganisms that cause various diseases and can be dangerous to human health. For this reason, the Public Health Institute performs seawater quality tests, from May to September where seawater quality data are available. In addition to the pollution and the number of microorganisms, seawater quality analyzes show climatic, geological and hydrological characteristics. In this paper seawater quality of some of the largest and most famous beaches of Zadar, Biograd, Nin and Pag were described. The analysis reviled that the quality of the mentioned beaches were mostly valued by excellent grades in 2017. However, due to the increasing number of tourists in this area, it is necessary to continuously monitor the quality of seawater to respond as soon as possible, if pollution occurs.