Disclosed herein is an image encoding/decoding method and apparatus. The image decoding method includes deriving an intra prediction value by performing intra prediction with respect to a current block, deriving an inter prediction value by performing inter prediction with respect to the current block, deriving a combined inter intra prediction (CIIP) value by weighting the intra prediction value and the inter prediction value, and generating a reconstructed block of the current block using the CIIP value. The intra prediction is performed in a Planar mode.