Provided is a method for modifying a polypropylene resin molded body with a side chain crystalline block copolymer having a long alkane chain in a side chain, having a good interaction force with the polypropylene resin molded body, and having a function capable of modifying surface characteristics. Also provided is a modified polypropylene resin molded body. The method for modifying a polypropylene resin molded body includes a step of contacting a copolymer solution including a side chain crystalline block copolymer with a polypropylene resin molded body at a temperature of the copolymer solution of 40 to 120° C. The modified polypropylene resin molded body includes a base material of the polypropylene resin molded body and a site that includes the side chain crystalline block copolymer in at least part of the base material.