The object of the present invention is to provide a masking member(11) which has good heat resistance and can be used repeatedly.To attain this object, the present invention provides a masking member made of a polymer alloy having a sea-island structure containing polyolefin in a continuous phase and one or more kind(s) of engineering plastic selected from among a group consisting of methyl pentene copolymer, polysulphone, polyethersulphone, polyphenylenesulphide, polyphenyleneether, polyamideimide, polyetherimide, and polyether-etherketone in a dispersed phase.