A hydraulic machine comprising: a first working fluid supply, with a maximum flow rate dischargeable therefrom being equal to a first capacity; a second working fluid supply; a first working fluid path extending from the first working fluid supply; a second working fluid path extending from the second working fluid supply; a confluence path connecting the first working fluid path and the second working fluid path to selectively allow working fluid from the second working fluid path to be combined with working fluid in the first working fluid path; a first flow control valve located on the first working fluid path to be movable from a first position to a second position to direct working fluid from the first working fluid path to a first actuator; a second flow control valve located on the second working fluid path to be movable from a first position to a second position to direct working fluid from the second working fluid path to a second actuator; a first manipulator generating a first signal to adjust a displacement of the first flow control valve; a second manipulator generating a second signal to adjust a displacement of the second flow control valve; and a controller, wherein the first actuator comprises an option actuator, with a maximum flow rate allowed to be supplied thereto being preset to be a first maximum allowable flow rate, and characterised in that the controller controls the first working fluid supply and the second working fluid supply such that the first working fluid supply discharges working fluid at a flow rate equal to the first capacity and the second working fluid supply discharges working fluid at a flow rate obtained by deducting the first capacity from the first maximum allowable flow rate when the first maximum allowable flow rate is higher than the first capacity, a value of the first signal is a maximum level, and a value of the second signal is equal to or higher than a minimum level and equal to or lower than a maximum level. a first working fluid supply, with a maximum flow rate dischargeable therefrom being equal to a first capacity; a second working fluid supply; a first working fluid path extending from the first working fluid supply; a second working fluid path extending from the second working fluid supply; a confluence path connecting the first working fluid path and the second working fluid path to selectively allow working fluid from the second working fluid path to be combined with working fluid in the first working fluid path; a first flow control valve located on the first working fluid path to be movable from a first position to a second position to direct working fluid from the first working fluid path to a first actuator; a second flow control valve located on the second working fluid path to be movable from a first position to a second position to direct working fluid from the second working fluid path to a second actuator; a first manipulator generating a first signal to adjust a displacement of the first flow control valve; a second manipulator generating a second signal to adjust a displacement of the second flow control valve; and a controller, wherein the first actuator comprises an option actuator, with a maximum flow rate allowed to be supplied thereto being preset to be a first maximum allowable flow rate, and characterised in that the controller controls the first working fluid supply and the second working fluid supply such that the first working fluid supply discharges working fluid at a flow rate equal to the first capacity and the second working fluid supply discharges working fluid at a flow rate obtained by deducting the first capacity from the first maximum allowable flow rate when the first maximum allowable flow rate is higher than the first capacity, a value of the first signal is a maximum level, and a value of the second signal is equal to or higher than a minimum level and equal to or lower than a maximum level.