Provided are an LDPC decoding apparatus and method using a sequential decoding algorithm having a partial group, capable of reducing the number of an iterative decoding by more than half without degrading the performance and increasing an amount of computation. The LDPC decoding method includes the steps of: receiving a prior probability information (channel values) based on information on channel values associated with distance between symbol signals in constellation related to the received noise and LDPC encoded data, and initializing bit nodes; dividing check nodes into partial groups before updating check node information based on the prior probability information, and performing a decoding by applying a sequential decoding algorithm; determining whether a parity check equations are satisfied; and outputting decoded messages obtained when satisfying the parity check equation or after terminating an iterative processor by a termination algorithm.