Provided are an image encoding/decoding method and apparatus. An image decoding method performed by an image decoding apparatus may comprise determining an intra prediction mode of a current block, performing planar intra prediction based on the intra prediction mode being a planar prediction mode and obtaining a reconstructed sample of the current block based on a prediction sample obtained based on the planar intra prediction. The performing the planar intra prediction may comprise applying filtering to an intra prediction reference sample of the current block.