A working machine comprising a body including an upperstructure, a working device attached to the body, the working device including a boom connected to the body so as to be rotatable in an up/down direction, an arm connected to a distal end of the boom so as to be rotatable in the up/down direction, a boom cylinder driving the boom, and an arm cylinder driving the arm, a swing motor which drives the upperstructure, and a hydraulic drive device comprising: a first hydraulic pump and a second hydraulic pump which supply pressure oil for operating the boom cylinder and the arm cylinder, respectively; a first boom directional control valve and a second arm directional control valve connected in parallel to the first hydraulic pump so that the first boom directional control valve controls a flow of the pressure oil supplied to the boom cylinder and the second arm directional control valve controls a flow of the pressure oil supplied to the arm cylinder; a second boom directional control valve and a first arm directional control valve connected in parallel to the second hydraulic pump so that the second boom directional control valve controls a flow of the pressure oil supplied to the boom cylinder and the first arm directional control valve controls a flow of the pressure oil supplied to the arm cylinder; and a third hydraulic pump, characterized in that the hydraulic drive device includes: the third hydraulic pump supplying pressure oil for operating the boom cylinder, the arm cylinder, and the swing motor; a swing directional control valve connected to the third hydraulic pump so as to control a flow of the pressure oil supplied to the swing motor; a third boom directional control valve connected to the third hydraulic pump in parallel to the swing directional control valve so as to control a flow of the pressure oil supplied to the boom cylinder; and a third arm directional control valve connected in tandem with the third boom directional control valve on the downstream side so as to control a flow of the pressure oil supplied to the arm cylinder. a first hydraulic pump and a second hydraulic pump which supply pressure oil for operating the boom cylinder and the arm cylinder, respectively; a first boom directional control valve and a second arm directional control valve connected in parallel to the first hydraulic pump so that the first boom directional control valve controls a flow of the pressure oil supplied to the boom cylinder and the second arm directional control valve controls a flow of the pressure oil supplied to the arm cylinder; a second boom directional control valve and a first arm directional control valve connected in parallel to the second hydraulic pump so that the second boom directional control valve controls a flow of the pressure oil supplied to the boom cylinder and the first arm directional control valve controls a flow of the pressure oil supplied to the arm cylinder; and a third hydraulic pump, characterized in that the hydraulic drive device includes: the third hydraulic pump supplying pressure oil for operating the boom cylinder, the arm cylinder, and the swing motor; a swing directional control valve connected to the third hydraulic pump so as to control a flow of the pressure oil supplied to the swing motor; a third boom directional control valve connected to the third hydraulic pump in parallel to the swing directional control valve so as to control a flow of the pressure oil supplied to the boom cylinder; and a third arm directional control valve connected in tandem with the third boom directional control valve on the downstream side so as to control a flow of the pressure oil supplied to the arm cylinder. the third hydraulic pump supplying pressure oil for operating the boom cylinder, the arm cylinder, and the swing motor; a swing directional control valve connected to the third hydraulic pump so as to control a flow of the pressure oil supplied to the swing motor; a third boom directional control valve connected to the third hydraulic pump in parallel to the swing directional control valve so as to control a flow of the pressure oil supplied to the boom cylinder; and a third arm directional control valve connected in tandem with the third boom directional control valve on the downstream side so as to control a flow of the pressure oil supplied to the arm cylinder.