Abstract: The present invention relates to an image encoding/decoding method and device. The image decoding method according to the present invention comprises the steps of: decoding a prediction mode index; determining whether the prediction mode index indicates function-based intra prediction; inducing a parameter (s) for generating a function, when the prediction mode index indicates the function-based intra prediction; generating the function on the basis of the induced parameter (s); and performing intra prediction by using the generated function.