PROBLEM TO BE SOLVED: To provide a gel composition for an ultrasonic medium, which forms a uniform film between an ultrasonic generator and the skin and efficiently transmits ultrasonic waves to the skin.SOLUTION: The gel composition contains a component (A) of an alkyl-modified carboxy vinyl polymer and/or its salt, a component (B) of a carboxy vinyl polymer and/or its salt, a component (C) of a hydroxyalkyl cellulose, a component (D) of a polyacrylic acid and/or its salt and a component (E) of a polyhydric alcohol.