A vector code book (1094) where representative samples of vectors to be quantized are stored is created. Each vector is made up of three elements: an AC gain, a value corresponding the logarithm of an SC gain, and an adjustment coefficient of the prediction coefficient of SC. Coefficients for predictive coding are stored in a prediction coefficient storage section (1095). The coefficients are the prediction coefficients of MA, and two kinds of coefficients, AC and SC for the order of prediction are stored. A parameter calculating section (1091) calculates a parameter necessary for distance calculation from an auditory sensation weighting input voice, an adaptive sound source subjected to auditory weighting LPC synthesis, a probabilistic sound source subjected to auditory sensation weighting LPC synthesis, a decoded vector (AC, SC, adjustment coefficient) stored in a decoded vector storage section (1096), and the prediction coefficients (AC, SC) stored in the prediction coefficient storage section (1095).