A method and an apparatus for encoding/decoding key value data of a coordinate interpolator used in a three-dimensional graphic animation are provided. The apparatus for encoding key value data of a coordinate interpolator representing the position of each vertex of an object using coordinates of each of the vertices including x, y, and z components includes a quantizer, which quantizes a coordinate interpolator input thereinto with predetermined quantization bits, a DPCM processor, which performs a DPCM operation of a predetermined mode on each component of each vertex of the quantized coordinate interpolator and thus generates differential data based on the temporal variation of the coordinates of each of the vertices and differential data based on the spatial variation of the coordinates of each of the vertices, a dictionary encoder, which generates symbols representing the differential data of each of the components of each of the vertices and the mode of a DPCM operation which has been performed on the differential data and position indexes indicating the positions of the symbols, and an entropy encoder, which entropy-encodes the symbols and the position indexes.