Disclosed herein is a flat panel display device capable of reducing switching noise and electromagnetic interference noise caused by driving of a multiplexer and stabilizing a common voltage in an in-cell touch flat panel display device. Discloses is a multiplexer controlled by k MUX control signals and k pseudo MUX control signals to selectively supply the data signal supplied from each output channel of the data driving circuit to k data lines. The multiplexer includes k pairs of switching transistors. Each pair of switching transistors include a first switching transistor controlled by one of the k MUX control signals to supply a data signal output from the one output channel of the data driving circuit to one data line, and a second switching transistor controlled by one of the k pseudo MUX control signals having a phase opposite to that of the one of the k MUX control signals.