There is provided a decoding apparatus that decodes data encoded by transform coding in units of predefined image areas, including a coefficient setting unit that sets modification coefficients for each of the image areas; and a dequantized value generating unit that generates a dequantized value corresponding to a first quantized index value of a target area which is an image area to be modified, based on the first quantized index value of the target area, a second quantized index value of other image area in predetermined relative position to the target area, and the modification coefficients set by the coefficient setting unit.