HYDRAULIC MACHINE

A hydraulic machine comprises: a tank (101); a working device including a boom; a boom cylinder which operates the boom and has a large chamber (313a) and a small chamber (313b); a floating hydraulic circuit connected to the large chamber (313a), the small chamber (313b), and the tank (101) so as to perform a floating function which enables the large chamber (313a), the small chamber (313b), and the tank (101) to communicate with each other; and an operator input device for receiving, from a driver, a request for turning on or turning off the floating hydraulic circuit. In the case of a boom down operation for lowering the boom, it is determined whether the working device floats in the air, and when it is determined that the working device floats in the air, the floating hydraulic circuit can be turned off, even if the request for turning on the floating hydraulic circuit is input to the operator input device. In some embodiments, when a value (the pressure of the large chamber (313a) - the pressure of the small chamber (313b)/(a valid area to which the pressure of the large chamber (313a) is applied/a valid area to which the pressure of the small chamber (313b) is applied)) is greater than a preset value, it may be determined that the working device floats in the air. In some alternative embodiments, when the value of the pressure of the large chamber (313a) is greater than the preset value, it may be determined that the working device floats in the air.