Pump controller: when operation device receives neither first or second operation, outputs standby rotation speed as command rotation speed to engine controller, standby rotation speed being lower than selected reference rotation speed; when operation device receives first operation, changes command rotation speed from standby rotation speed to first target rotation speed in such a manner that as an amount of first operation increases, increasing rate of command rotation speed decreases gradually; when operation device receives second operation, changes command rotation speed from standby rotation speed to second target rotation speed in such a manner that as an amount of second operation increases, increasing rate of command rotation speed increases gradually; and feeds command current to a solenoid proportional valve that outputs secondary pressure to regulator that adjusts tilting angle of a pump, such that a discharge flow rate of the pump is proportional to amount of first and second operation.