A control unit for an internal combustion engine, comprising: a valve opening/closing timing control apparatus including: a driving side rotary body rotatable about a rotational axis in synchronism with a crankshaft of an internal combustion engine; a driven side rotary body mounted rotatably about the same axis as the rotational axis relative to the driving side rotary body, the driven side rotary body being rotatable together with an exhaust cam shaft controlling opening/closing of an exhaust valve of the internal combustion engine; and a phase adjustment mechanism configured to set a relative rotational phase between the driving side rotary body and the driven side rotary body; the exhaust cam shaft being configured to open/close the exhaust valves of a plurality of cylinders with a predetermined rotational angular spacing therebetween; after an opening timing of the exhaust valve, an advancing operation being effected to displace the relative rotational phase in an advancing direction relative to the opening timing; and subsequently, the relative rotational phase being displaced in a direction of a retarding operation releasing the advancing operation in order to cause the exhaust valve of another cylinder which is to effect an exhaust operation next to open at an original opening timing, wherein: the phase adjustment mechanism sets the relative rotational phase between the driving side rotary body and the driven side rotary body by an electrically powered actuator; there is provided a controlling section controlling the electrically powered actuator; the internal combustion engine is set such that the respective exhaust valves of the plurality of cylinders controlled by the exhaust cam shaft are not opened simultaneously; and a control mode of the controlling section is set such that the retarding operation is initiated from the closing timing of the exhaust valve. a valve opening/closing timing control apparatus including: a driving side rotary body rotatable about a rotational axis in synchronism with a crankshaft of an internal combustion engine; a driven side rotary body mounted rotatably about the same axis as the rotational axis relative to the driving side rotary body, the driven side rotary body being rotatable together with an exhaust cam shaft controlling opening/closing of an exhaust valve of the internal combustion engine; and a phase adjustment mechanism configured to set a relative rotational phase between the driving side rotary body and the driven side rotary body; a driving side rotary body rotatable about a rotational axis in synchronism with a crankshaft of an internal combustion engine; a driven side rotary body mounted rotatably about the same axis as the rotational axis relative to the driving side rotary body, the driven side rotary body being rotatable together with an exhaust cam shaft controlling opening/closing of an exhaust valve of the internal combustion engine; and a phase adjustment mechanism configured to set a relative rotational phase between the driving side rotary body and the driven side rotary body; the exhaust cam shaft being configured to open/close the exhaust valves of a plurality of cylinders with a predetermined rotational angular spacing therebetween; after an opening timing of the exhaust valve, an advancing operation being effected to displace the relative rotational phase in an advancing direction relative to the opening timing; and subsequently, the relative rotational phase being displaced in a direction of a retarding operation releasing the advancing operation in order to cause the exhaust valve of another cylinder which is to effect an exhaust operation next to open at an original opening timing, wherein: the phase adjustment mechanism sets the relative rotational phase between the driving side rotary body and the driven side rotary body by an electrically powered actuator; there is provided a controlling section controlling the electrically powered actuator; the internal combustion engine is set such that the respective exhaust valves of the plurality of cylinders controlled by the exhaust cam shaft are not opened simultaneously; and a control mode of the controlling section is set such that the retarding operation is initiated from the closing timing of the exhaust valve. the phase adjustment mechanism sets the relative rotational phase between the driving side rotary body and the driven side rotary body by an electrically powered actuator; there is provided a controlling section controlling the electrically powered actuator; the internal combustion engine is set such that the respective exhaust valves of the plurality of cylinders controlled by the exhaust cam shaft are not opened simultaneously; and a control mode of the controlling section is set such that the retarding operation is initiated from the closing timing of the exhaust valve.