A video signal processing device is configured to include a quantizer that sequentially outputs quantized data obtained by quantizing input data based on the video data of the first gradation into the video data of the second gradation, a storage that sequentially stores the quantized data output from the quantizer, a difference calculator that sequentially calculates differences between the video data of the first gradation for a current frame and the quantized data for a previous frame stored in the storage, and an integrator that sequentially outputs integral data obtained by sequentially integrating data output from the difference calculator as the input data of the quantizer.