A skin patch that can enhance the water resistance and handling easiness and can alleviate any irritation on the user. There is provided a skin patch having a flexible backing and, superimposed thereon, a plaster containing a styrene-isoprene-styrene block copolymer and having a glass transition temperature (Tg) of -45.degree. to -35.degree. C. and tan .delta. (lag angle) value, determined at dynamic viscoelasticity measurement (frequency 6.2832 rad/s) at 45.degree. C., of 0.25 or less.