According to an embodiment, a control device includes a receiving unit, a judging unit, an estimating unit, a deciding unit, a directing unit, and a sending unit. The receiving unit is configured to receive an interrupt request requesting a processing device that includes elements capable of being individually subjected to voltage control to execute an interrupt process. The judging unit is configured to judge a state of the elements. The estimating unit is configured to estimate a start-up time for the element to change into an operating mode after power is supplied. The deciding unit is configured to decide a starting point in time at which power supply is to be started on basis of a difference in the start-up times between the elements. The directing unit is configured to direct a power supply unit for supplying power to the elements. The sending unit is configured to send the interrupt request.