There is provided a control device which controls a transformer in accordance with a total loss imposed on a load driving system including the transformer and a load. In a control device of a transformer that boosts or drops an output voltage of a DC power supply and provides the output voltage to a load, the control device includes: a switching controller which performs switching control of the transformer; a load power deriving unit which derives load power; a transformer loss decrease amount deriving unit which derives a decrease amount of loss generated in the transformer, based on the load power derived by the load power deriving unit and a transformer ratio of the transformer, when the switching controller performs intermittent control of the transformer; a load loss increase amount deriving unit which derives an increase amount of loss generated in the load when the switching controller performs the intermittent control of the transformer; and a control command unit which instructs the switching controller to perform the intermittent control of the transformer when the decrease amount of transformer loss derived by the transformer loss decrease amount deriving unit is larger than the increase amount of load loss derived by the load loss increase amount deriving unit.