A moving picture encoding apparatus divides a moving picture signal into key frames and non-key frames, encodes the key frames, predicts the non-key frames from the encoded key frames, determines an encoding rate for each non-key frame, encodes each non-key frame, and outputs an error-correcting code at the encoding rate as encoded data of the non-key frame. To determine the encoding rate, parameters related to the likelihood of prediction errors are calculated by at least two different methods for each non-key frame, the parameters are compared, one of the parameters is selected, and the encoding rate is calculated from the selected parameter. The selective use of differently calculated parameters enables an efficient encoding rate to be calculated for each non-key frame and reduces the transmission of encoded data that the decoder does not need or cannot decode.