The invention relates to water dispensers, in particular to an overflow-proof water dispenser where water in a bucket cannot flow out when water in a water storage tank reaches an extreme water level. The overflow-proof water dispenser comprises a shell, a seesawing rod and a floater connected at one end of the seesawing rod, a bucket bearing seat, a water outgoing faucet and the water storage tank are arranged in the shell, a water incoming rod is arranged in the bucket bearing seat, the water outgoing faucet and the water incoming rod are communicated through a water pipe, the floater is positioned in the water storage tank, an overflow control valve is arranged in the water pipe, is a normally-open valve and comprises a pressing handle, a pressing portion is arranged at the other end of the seesawing rod, and a water storage extreme position is arranged in the water storage tank. When the water in the water storage tank reaches the water storage extreme position, the pressing portion presses the pressing handle to enable the overflow control valve to be closed. By the overflow-proof water dispenser, the problem that water in a water storage tank overflows on the ground due to the fact that water in a bucket continues flowing out after the water storage tank of an existing water dispenser is filled with water is solved.