A print data generating device is configured to generate print data for creating a printed medium by printing a target image on a heat-sensitive medium with a printing device. The printing device includes a thermal head having a heating element. The heat-sensitive medium includes: a base material; and a heat-sensitive layer. The base material has a transparency. The heat-sensitive layer is provided over one surface of the base material and is configured to develop a first color when heated to a first temperature or higher. The printing device is configured to control the heating element according to the print data to heat the heat-sensitive medium. The print data generating device includes a controller. The controller is configured to perform: (a) determining a condition of a background area on which the heat-sensitive medium is to be superimposed; and (b) generating the print data in accordance with the condition determined in (a).