The present invention is to reduce the flow rate of pressure oil discharged from a main pump and returned to a tank when specific work is executed with an operation amount of an operating device being made small in the state in which an engine is kept at an idling speed. According to the present invention, there is provided a main controller (20) which is capable of controlling the speed of an engine (11) to a normal work speed at which a work implement such as a boom (4) can perform normal work and which controls the speed of the engine (11) to an idling speed serving as a speed lower than the normal work speed when an operating device has returned from an operating position to a neutral position. Configuration is made such that the main controller (20) performs a control process for bringing the speed of the engine (11) to a specific work speed serving as a speed higher than the idling speed but lower than the normal work speed, on detecting execution of the specific work which is performed with an operation amount of the operating device such as a boom operating device (16) being kept small in a state in which the speed of the engine (11) is kept at the idling speed.