A laundry treatment apparatus and a controlling method thereof are disclosed. The laundry treatment apparatus includes a leakage detecting device detecting washing water leaking to the lower side of a casing, an auxiliary power supply recharged when a main electric power is supplied, and a controller controlling the auxiliary electric power supply according to the detection by the leakage detecting device. According to the leakage controlling method, since the external electric power inputted to the laundry treatment apparatus is interrupted and the auxiliary power supply is recharged during the supplying of the main electric power to the laundry treatment apparatus when the leakage is detected, an electric leakage and other accidents can be prevented, and an informing device is controlled by the auxiliary power supply so that the leakage can be measured.