1. A vector quantizer for processing color video signals, comprising; an input vector register for receiving an input vector X composed of a block of K (K being more than one) samples including at least two color video signals from each of three channels; an output vector code table memory for particitioning a signal space S.sup.k of said input vector into subspaces having minimum distorted partition and which stores a set of the representative points of said subspaces produced as output vectors; a mini-max arithmeticoperator that detects an output vector which, as a result of mini-max approximation, has been found to be the least distorted from the input vector from among the output vectors successively read from said codetable memory; a coder for encoding the address of said least distorted output vector in said codetable and for delivering the coded address as an output signal; a decoder for reading a corresponding output vector from a decoding output vector code memory using said coded output signal as an address signal; and an output vector decomposing register that decomposes the output vector from said decoder into three channels of output signal sequence.