An encoding device includes: a difference generation unit for obtaining a first pixel difference value as a difference value between a first pixel value and a pixel value of a pixel having the same color as the first pixel positioned in the vicinity of the first pixel; a quantization width decision unit for deciding a quantization width in data generation by quantizing the first and the second pixel value according to the number of digits of an unsigned integer binary value of the first pixel difference value and the number of digits of an unsigned integer binary value of the second pixel difference value generated in the difference generation unit for the second pixel value of the second pixel; a quantization width information generation unit for generating quantization width information having a quantization width used for quantization/decoding of the first and the second pixel value; and a quantization unit for generating a first and a second compressed encoded pixel value of n-bit length.