This research aims to study the appearance quantity and quality of cassava of Gatotkaca variety with different age of harvest in Gunungkidul regency. The research was conducted from September 2017 to June 2018 located in Ponjong subdistrict, Gunungkidul Regency, D.I Yogyakarta Province and the Research Laboratory of Agriculture Faculty University of Muhammadiyah Yogyakarta. The experiment was done by using field experimental method with a single factor arranged by Randomized Complete Block Design (RCBD). The treatment tested was harvest age which consisted of 6 treatments, namely age of harvest 4 months (January), 5 months (February), 6 months (March), 7 months (April), 8 months (May), and 9 months (June). Observation variables were carried out on the growth of the Gatotkaca variety cassava plants include: ie cassava plant height, number of leaves and stem diameter and components yield of Gatotkaca variety of cassava plants include: ie number of cassava tubers, cassava tubers length, cassava tubers diameter, cassava tubers weight per plant, cassava tubers yield, content of starch and HCN. The results showed that the harvest age of gatotkaca varieties cassava 9 months after planting showed a maximum yield quantity of 43,100 Ton / Ha, while the HCN quality was lowest (7, 38 ppm) and maximum starch content (30.85%).