1. An intra prediction method of predicting pixel values in a prediction target block on the basis of a plurality of neighboring pixels adjacent to the prediction target block, comprising the steps of: receiving and decoding encoded video information; determining a target boundary by determining a plurality of boundary pixels indicating a target boundary in the prediction target block on the basis of the decoded video information; determining a plurality of prediction target regions into which the prediction target block is split by the target boundary; and performing a prediction on the plurality of prediction target regions on the basis of different neighboring pixels out of the plurality of neighboring pixels, wherein the plurality of boundary pixels include N boundary pixels {p 0 , p 1 ,. .. , p n ,. .. , p N-1 }, N is a positive integer, and n is an integer of 0 to N−1, wherein the video information includes information indicating a chain code corresponding to the boundary pixel p n , wherein the chain code indicates an angle between a first progress direction from the boundary pixel pn−1 to the boundary pixel p n and a second progress direction from the boundary pixel p n to the boundary pixel p n+1 , wherein the chain code is selected from a chain code group comprising 7 chain codes including a first chain code representing 0 degree, a second chain code representing 45 degree, a third chain code representing −45 degree, a fourth chain code representing 90 degree, a fifth chain code representing −90 degree, a sixth chain code representing 135 degree and a seventh chain code representing −135 degree, and wherein the first chain code is represented by a binary code “0”, the second chain code is represented by a binary code “10”, the third chain code is represented by a binary code “110”, the fourth chain code is represented by a binary code “1110”, the fifth chain code is represented by a binary code “11110”, the sixth chain code is represented by a binary code “111110” and the seventh chain code is represented by a binary code “111111”.