A data decoding device capable of decoding plural kinds of data superimposed in a vertical blanking period of a video signal. The device comprises means for detecting the line number and the intraline position in the vertical blanking period from vertical and horizontal sync signals and generating a line signal extract pulse, a data signal extract pulse and a reference signal extract pulse; binary circuit means for converting the video signal into a binary signal; PLL means for producing a data extract clock signal in synchronism with a clock reference signal extracted on the basis of the line signal extract pulse and the reference signal extract pulse; memory means supplied with the data extract clock signal and the binary signal in response to the line signal extract pulse and the data signal extract pulse, and storing the data signal therein; and control means capable of designating a plurality of durations for generating the respective extract pulses and a plurality of frequency division ratios in the PLL means. In the device, the circuits are usable in common to achieve curtailment in the production cost.