The objective of the present invention is to perform fast variable-length coding that is applied for lossless compression and encoding. To achieve this objective, an encoding device comprises a unit for determining, from a plurality of states, states of peripheral pixels of an object pixel to be encoded, a unit for producing a predicted value of the object pixel based on the peripheral pixels, a memory used for storing a k parameter (k≦0) for each of the plurality of states, a unit for encoding a prediction difference between the value of the object pixel and a predicted value to variable-length code having a code length that is obtained by using the prediction difference and the k parameter that is stored in the memory and corresponds to the state determined by the state determination unit and a unit for, after variable-length encoding is performed for the object pixel, updating in advance the k parameter in order to perform variable-length encoding for another pixel that has the same state as the state determined by the state determination unit, and for writing the k parameter to the memory.