A control device of controlling a liquid droplet ejection head includes a head substrate; a head controller applying a drive voltage to the head substrate to control the ejection of liquid droplets; a relay substrate connecting the head substrate and the head controller; a main-body controller controlling the head controller; and a voltage conversion circuit disposed in the relay substrate. Further, the voltage conversion circuit converts a resistance value in accordance with a temperature of the head substrate into an output voltage, the relay substrate inputs the output voltage into the main-body controller, and the main-body controller detects the temperature based on the output voltage and determines the drive voltage based on the detected temperature.