We show that ultrasound can induce Shapiro steps (SSs) in a charge-density-wave (CDW) state. When ultrasound with frequency ω and a dc voltage are applied, the SSs occur at the current I [Formula: see text] with an integer n. Even and odd multiples of SSs are represented by two couplings between the CDW and ultrasound. Although an ac voltage bias with frequency ω induces the SSs at [Formula: see text], the ultrasound bias enhances the odd multiples more strongly than the even ones. This is the difference between the ultrasound and the ac voltage. Since the SSs cause abrupt peaks in the dV/ dI, the extreme changes in the I–V curve will be applied to a very sensitive ultrasound detector.