A control apparatus for an engine, the control apparatus being configured to control the engine, the engine comprising: an exhaust-driven supercharger having an adjusting mechanism at an exhaust passage, the adjusting mechanism being configured to change a supercharging efficiency according to an opening degree (Avn), control modes of the adjusting mechanism including a first control mode and a second control mode, the first control mode allowing the opening degree (Avn) to be maintained at a maximum supercharging efficiency opening degree (Avnmax) at which the exhaust-driven supercharger has a maximum supercharging efficiency independently of a deviation (ΔPim) between a target supercharging pressure (Pimtg) and an actual supercharging pressure (Pim), the second control mode allowing the deviation to be fed back to the opening degree (Avn); and an electrically-driven supercharger which is driven by an electrical power supplied from an electrical power supply, the control apparatus comprising: a stopping device which is configured to stop the supply of the electrical power to the electrically-driven supercharger, when the deviation (ΔPim) reaches a first reference value (ΔPim_0) or a time during which the electrical power is supplied to the electrically-driven supercharger reaches a predetermined time (tec1_0) during a period during which the actual supercharging pressure (Pim) increases; a determining device which is configured to determine whether or not the supply of electrical power to the electrically-driven supercharger stops; and a maintaining device which is configured to maintain the control mode in the first control mode until it is determined by the determining device that the supply of the electrical power to the electrically-driven supercharger stops. an exhaust-driven supercharger having an adjusting mechanism at an exhaust passage, the adjusting mechanism being configured to change a supercharging efficiency according to an opening degree (Avn), control modes of the adjusting mechanism including a first control mode and a second control mode, the first control mode allowing the opening degree (Avn) to be maintained at a maximum supercharging efficiency opening degree (Avnmax) at which the exhaust-driven supercharger has a maximum supercharging efficiency independently of a deviation (ΔPim) between a target supercharging pressure (Pimtg) and an actual supercharging pressure (Pim), the second control mode allowing the deviation to be fed back to the opening degree (Avn); and an electrically-driven supercharger which is driven by an electrical power supplied from an electrical power supply, the control apparatus comprising: a stopping device which is configured to stop the supply of the electrical power to the electrically-driven supercharger, when the deviation (ΔPim) reaches a first reference value (ΔPim_0) or a time during which the electrical power is supplied to the electrically-driven supercharger reaches a predetermined time (tec1_0) during a period during which the actual supercharging pressure (Pim) increases; a determining device which is configured to determine whether or not the supply of electrical power to the electrically-driven supercharger stops; and a maintaining device which is configured to maintain the control mode in the first control mode until it is determined by the determining device that the supply of the electrical power to the electrically-driven supercharger stops. a stopping device which is configured to stop the supply of the electrical power to the electrically-driven supercharger, when the deviation (ΔPim) reaches a first reference value (ΔPim_0) or a time during which the electrical power is supplied to the electrically-driven supercharger reaches a predetermined time (tec1_0) during a period during which the actual supercharging pressure (Pim) increases; a determining device which is configured to determine whether or not the supply of electrical power to the electrically-driven supercharger stops; and a maintaining device which is configured to maintain the control mode in the first control mode until it is determined by the determining device that the supply of the electrical power to the electrically-driven supercharger stops.