An intra prediction method includes searching for a neighboring block restored prior to a current block from among blocks of an image; checking whether the neighboring block found by the searching is a block restored in an intra mode and whether an intra mode of the current block is also a Combined Intra Prediction (CIP) mode in which only blocks pre-restored in the intra mode are referred to; determining based on a checking result of the checking whether the found neighboring block is a reference block available for intra prediction of the current block; and performing intra prediction on the current block by using sample values of the reference block determined as available for the intra prediction of the current block.