A vibrating device includes a dust-screening member shaped like a plate as a whole, a first vibrating member secured to the dust-screening member and configured to cause, when driven alone, the dust-screening member to undergo first standing-wave vibration, and a second vibrating member secured to the dust-screening member and configured to cause, when driven alone, the dust-screening member to undergo second standing-wave vibration. The first vibrating member and the second vibrating member are so positioned that the first standing-wave vibration and second standing-wave vibration produced by the first and second vibrating members, respectively, overlap each other, thus producing a travelling wave propagating in one direction and having nodes regions at an outer circumferential edge of the dust-screening member, the node regions having virtually no vibrational amplitude.