An image forming device includes a communication unit to transmit data to and receive data from an external device, an image forming job unit to perform printing, and a controller to control warming up of the image forming job unit to perform the printing, such that the image forming job unit performs the printing after the warming up is completed. The controller is to receive a print execution request to perform the printing and a predicted value of a print preparation time for the image forming device to create output image data, to perform the printing, from the external device via the communication unit, determine a warm-up start time of when to start the warming up of the image forming job unit by using the received predicted value of the print preparation time, and control the image forming job unit to start the warming up at the determined warm-up start time.