Most cocoa beans in Indonesia are traditionally produced by farmers using non fermented and sun drying method. Thequality of cocoa beans produced by farmer in yogyakarta may be improved by the fermentation method. However, it needsoptimization for best fermentation process. The aims of the study was to improve quality of cocoa bans by fermentation ofsun dried cocoa beans. The characteric fermented cocoa beans was determined by maesuring changes pH, acidity andfermentation indexs of cocoa beans during fermentation. This study used preconditioned cocoa beans to resamble obtainfrom the farmer. Preconditioning was done in order to get 15% mouisture content of pulp at same level as moisture contentof pulp from traditional process. Before fermentation, therefor sun dried cocoa beans was rehydrated to obtain a moisturecontent of pulp similiar to fresh beans pulp, and then fermentation was conducted for 120 hours. Changes in acidity andfermentation indexs of cocoa beans during fermentation were measured. The fermentation process used 3 level treatmenti.e. control (without inoculum), mixed culture of microbies added at the begining fermentation. The result show all cocoabeans acidity increase during fermentation from 4,48% to 6,45% for control, 4,64% to 6,39% for addition of inoculum atbegining of fermentation and from 4,45% to 6,59% for addition of inoculum at the begining and midle of fermentation andfermentation indexs of cocoa beans increase for all level of inoculum addition i.e. 0,31 to 0,88 for control, 0,32 to 0,99 foraddition of inoculum at the beginning fermentation and 0,33 to 1,03 for addition of inoculum at the beginning and midle offermentation. The study indicated that addition of mix culture microbies in fermetation improved the quality of cocoabeans that characterized by pH, acidity and fermentation indexs of cocoa beans.