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 there into 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 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.