Disclosed is a suspended particle device having a higher response speed of particles upon shutdown of the device. The suspended particle device includes a first substrate; a first electrode arranged on a surface of the first substrate; a second substrate; a second electrode arranged on a surface of the second substrate; and a suspension arranged between the first substrate and the second substrate, in which the suspension includes particles and a disperse medium, the particles are dispersed in the disperse medium, an orientation of the particles is controlled by an alternate-current voltage to be applied between the first electrode and the second electrode, and “a” which represents a frequency of an alternate-current voltage in a driving period is greater than “b” which represents a frequency of an alternate-current voltage in a shutdown period.