A ship, comprising: a hull; an engine configured to propelling the hull; a harmful substance reducing device configured to reduce harmful substances contained in an exhaust gas discharged from the engine; and an engine output adjusting device configured to down-regulating an output of the engine to reduce an amount of exhaust gas discharged from the engine, when the hull is located in an emission control area where discharge of harmful substances is prohibited or at an ECA preliminary entry point, whereby the engine output adjusting device includes: a hull location acquiring module configured to communicate with a global positioning system or a hull operating controller for operating the hull to acquire location information of the hull; an ECA-hull relative location determining module configured to compare the location information of the hull with stored location information of the ECA to determine whether the hull is located in the ECA or at the ECA preliminary entry point; and an engine output factor adjusting module configured to communicate with the hull operating controller or an engine driving device for operating the engine to down-regulate an engine output factor related with the output of the engine so that an amount of exhaust gas discharged from the engine decreases, when the hull is located in the ECA or at the ECA preliminary entry point, characterised in that the engine output factor adjusting module down-regulates the engine output factor so that an amount of exhaust gas discharged from the engine is adjusted according to a capacity of the harmful substance reducing device, and wherein the engine output factor includes any one selected from the group consisting of linear velocity of the hull, revolutions per minute of the engine, a fuel amount of the engine, and an effective pressure of the engine. a hull; an engine configured to propelling the hull; a harmful substance reducing device configured to reduce harmful substances contained in an exhaust gas discharged from the engine; and an engine output adjusting device configured to down-regulating an output of the engine to reduce an amount of exhaust gas discharged from the engine, when the hull is located in an emission control area where discharge of harmful substances is prohibited or at an ECA preliminary entry point, whereby the engine output adjusting device includes: a hull location acquiring module configured to communicate with a global positioning system or a hull operating controller for operating the hull to acquire location information of the hull; an ECA-hull relative location determining module configured to compare the location information of the hull with stored location information of the ECA to determine whether the hull is located in the ECA or at the ECA preliminary entry point; and an engine output factor adjusting module configured to communicate with the hull operating controller or an engine driving device for operating the engine to down-regulate an engine output factor related with the output of the engine so that an amount of exhaust gas discharged from the engine decreases, when the hull is located in the ECA or at the ECA preliminary entry point, characterised in that the engine output factor adjusting module down-regulates the engine output factor so that an amount of exhaust gas discharged from the engine is adjusted according to a capacity of the harmful substance reducing device, and wherein the engine output factor includes any one selected from the group consisting of linear velocity of the hull, revolutions per minute of the engine, a fuel amount of the engine, and an effective pressure of the engine. a hull location acquiring module configured to communicate with a global positioning system or a hull operating controller for operating the hull to acquire location information of the hull; an ECA-hull relative location determining module configured to compare the location information of the hull with stored location information of the ECA to determine whether the hull is located in the ECA or at the ECA preliminary entry point; and an engine output factor adjusting module configured to communicate with the hull operating controller or an engine driving device for operating the engine to down-regulate an engine output factor related with the output of the engine so that an amount of exhaust gas discharged from the engine decreases, when the hull is located in the ECA or at the ECA preliminary entry point, characterised in that the engine output factor adjusting module down-regulates the engine output factor so that an amount of exhaust gas discharged from the engine is adjusted according to a capacity of the harmful substance reducing device, and wherein the engine output factor includes any one selected from the group consisting of linear velocity of the hull, revolutions per minute of the engine, a fuel amount of the engine, and an effective pressure of the engine.