An apparatus and a method for performing video decoding processes in parallel are provided. The method is adapted for utilizing a first cluster and a second cluster of a processor to perform the video data decoding process in parallel. The method includes performing a VLD process to the video data with the first cluster, so as to obtain a plurality of coefficients and then performing an IZ process, an IQ process, and an IDCT process to the coefficients with the second cluster, so as to obtain a plurality of pixels values of the video data. When the first cluster decodes a coefficient of the video data, the second cluster performs the IZ, IQ, and IDCT processes to a coefficient previously decoded by the second cluster of the video data. Accordingly, a parallel process is realized and the decoding speed is increased.