An apparatus for controlling an engine of construction equipment, wherein the engine is configured to generate power, the apparatus comprising: a vehicle control unit configured to control construction equipment; a lever configured to generate a first signal when a state of the construction equipment is switched to an operation state or a neutral state; an auto idle switch configured to generate a second signal when an auto engine idle mode is on; an engine control unit configured to control the engine by an engine speed command of the vehicle control unit, and generate engine torque information of the engine and provide the generated engine torque information to the vehicle control unit, wherein when a state of the lever is switched to a neutral state in an on state of the second signal, the vehicle control unit controls the engine control unit so that an engine speed of the engine is reduced to a step engine speed corresponding to a first speed reducing step, when the first speed reducing step is maintained for a predetermined time, the vehicle control unit controls the engine control unit so that the engine speed of the engine is further reduced to an idle engine speed corresponding to a second speed reducing step, and when a state of the lever is switched to an operation state while the second speed reducing step is maintained, characterised in that the vehicle control unit controls the engine control unit so that the engine speed of the engine is returned to the step engine speed corresponding to the first speed reducing step, wherein the step engine speed corresponding to the first speed reducing step is within a range equal to or higher than a minimum engine speed, at which operation performance of the construction equipment does no deteriorate, and equal to or lower than a rated engine speed. a vehicle control unit configured to control construction equipment; a lever configured to generate a first signal when a state of the construction equipment is switched to an operation state or a neutral state; an auto idle switch configured to generate a second signal when an auto engine idle mode is on; an engine control unit configured to control the engine by an engine speed command of the vehicle control unit, and generate engine torque information of the engine and provide the generated engine torque information to the vehicle control unit, wherein when a state of the lever is switched to a neutral state in an on state of the second signal, the vehicle control unit controls the engine control unit so that an engine speed of the engine is reduced to a step engine speed corresponding to a first speed reducing step, when the first speed reducing step is maintained for a predetermined time, the vehicle control unit controls the engine control unit so that the engine speed of the engine is further reduced to an idle engine speed corresponding to a second speed reducing step, and when a state of the lever is switched to an operation state while the second speed reducing step is maintained, characterised in that the vehicle control unit controls the engine control unit so that the engine speed of the engine is returned to the step engine speed corresponding to the first speed reducing step, wherein the step engine speed corresponding to the first speed reducing step is within a range equal to or higher than a minimum engine speed, at which operation performance of the construction equipment does no deteriorate, and equal to or lower than a rated engine speed.