Since one of the detergent-forming chemicals is phosphate, laundry wastewater contains this substance. In general, laundry businesses do not have waste treatment facilities, while high level of phosphate which is accumulated continuously in waters may lead to eutrophication that disrupting aquatic ecosystems and causing river sedimentation. One of the methods to decrease phosphate level from laundry wastewater is electrocoagulation, with aluminum plate as the electrode.The research was a true experiment and was aimed to know the decrease of phosphate levels in laundry wastewater yielded from “Rumah Laundry” located at Pajimatan, Imogiri, Bantu, after treated by electrocoagulation process with 3 pairs, 4 pairs and 5 pairs of aluminum electrode. The design of the research was pre-test post-test with control group in five times replications, on randomly selected treatment and control groups. The statistical test with paired t-test shows that the electrocoagulation process is able to reduce the phosphate levels in laundry waste water compared with those of the control (p-value < 0,05). By using the 3, 4, and 5 pairs of aluminium electrode, the reduction of phosphate levels were 31,4 %, 33,7 %, and 27,3 %, respectively. It can be seen that the effective decrease was from the 4 pairs of aluminium electrode with 12 volt voltage and 500 mA current strength. However, the one way Anava test on those results of the three different electrode pairs shows no significant differences (p-value > 0,05).