A variable length encoding apparatus such as an encoding apparatus using the MPEG standard, wherein without degrading the precision of quantization step, the generated code bit amount is limited. Encoding is performed at the quantization step of required picture quality by an encoding part 106, and a bit stream 141 is written in an external memory 101. The generated encoded bit amount is measured from the increment of a write pointer 121 increased because of the writing in the external memory 101 by a control unit 107. If the amount is larger than a preset value, the data is replaced with data leading to the same decoding result as those of the preceding or following reference picture by using a replacement pattern in accordance with the picture type and the position on a times series, and the data is written in the external memory 101, thus outputting the data as an output bit stream 111 controlled to the generated code amount within an upper limit value.