1. An image display medium driver comprising: a voltage applying unit that applies a writing pulse as a voltage between a pair of substrates of an image display medium that displays an image based on image information, the image display medium including a plurality of groups of colored particles colored in a color which is different for every group, enclosed between the pair of substrates, at least one of the substrates having transparent properties, each group of colored particles being moved when an absolute value of the voltage is equal to or higher than a threshold voltage, the threshold voltage being different for each group of the colored particles; and a controller that determines which of the substrates the colored particles are present on for each group of the colored particles based on a last image information used for displaying an image, and when the colored particles are present on both of the substrates, controls the voltage applying unit so as to apply a voltage having a smaller absolute value than any threshold voltage of the colored particles present on one of the substrates, and the voltage having a smaller absolute value is applied in a plurality of voltage pulses to create a particle adhering field extending in a direction from one of the substrates toward an other one of the substrates, and the voltage having a smaller absolute value is applied as the plurality of voltage pulses after the writing pulse and before a new writing pulse is applied, wherein the controller controls the voltage applying unit so as to apply a voltage having a smaller absolute value than any threshold voltage of the colored particles present on one of the substrates to create a particle adhering field extending in a direction from the one of the substrates toward the other one of the substrates and a voltage having a smaller absolute value than any threshold voltage of the colored particles present on the other one of the substrates to create a particle adhering field extending in a direction from the other one of the substrates toward the one of the substrates.