Study of Majorana nature of neutrinos is very important in fundamental physics, because it would clarify the extremely smallness of the neutrino mass and open the physics of very high-energy scale which might provide a key to solve the matter dominance of the current Universe. Neutrinoless double beta decay ($0¥nu¥beta¥beta$) of nucleus is a unique process to test the Majorana nature of neutrinos. KamLAND-Zen (KamLAND Zero-Neutrino Double-Beta Decay) is an experiment searching for $0¥nu¥beta¥beta$ of $^{136}$Xe nucleus using KamLAND detector in Kamioka mine in Japan. The experiment has provided the most stringent limit on the $^{136}$Xe $0¥nu¥beta¥beta$ lifetime of $1.07¥times10^{26}$ yr (90¥% C.L.) corresponding to the upper limit (90¥% C.L.) of the effective Majorana neutrino mass $¥langle m_{¥beta¥beta} ¥rangle$$<(61-165)$meV. In this talk current status and future plan of the KamLAND-Zen experiment are reported.