A dust-screening member is shaped like a plate as a whole, and has at least one side that is symmetric with respect to a virtual axis on a surface of the member. A vibrating member is adjacent to one side of the dust-screening member, arranged on the surface along the one side, and configured to produce, at the surface, vibration having a vibrational amplitude perpendicular to the surface. A drive unit is configured to drive the vibrating member to produce the vibration on the surface, such that peak ridges of the vibration form a closed loop and an area including a center of the closed loop is surrounded by a node area having almost no vibrational amplitude. When a thickness of the dust-screening member is assumed to be tg and a thickness of the vibrating member is assumed to be tp, tg/tp has a dimension of 0.8.