Method of orthogonal transform coding/decoding

There is provided the method of orthogonal transform coding/decoding to quantize/de-quantize transformed coefficients which are divided into a plurality of bands to which respective different numbers of coefficient are allotted. Quantization/de-quantization tables are arranged on the basis of a probability density function of the coefficient values designed on the assumption of a specified number of coefficients so as to correspond to the number of quantization/de-quantization bits. The values in the quantization/de-quantization tables selected according to the number of quantization/de-quantization bits are adaptivety compensated on the basis of an actual number of coefficients on each band to quantize/de-quantize the coefficient values.