A double-arm working machine comprising: a lower travel structure with a travel device; an upper bodywork that is provided at an upper section of the lower travel structure and includes an operator cabin; left and right swing posts (7a, 7b) provided on front left and right sides of the upper bodywork such that the swing posts (7a, 7b) each swing in both leftward and rightward directions; left and right work fronts (A, B) provided on the left and right swing posts (7a, 7b) such that the work fronts (A, B) each sway vertically; operating devices (50a, 50b) which each give an operational instruction to the swing post (7a, 7b) and the work fronts (A, B); and swing post angle sensors (67a, 67b) which each sense a swinging angle of the left or right swing post (7a, 7b); the working machine characterized by comprising an interference prevention controller (61F; 61FA) which, pursuant to a differential angle (θc) between the left and right work fronts (A, B) that has been calculated from sensor signals sent from the swing post angle sensors (67a, 67b), and to a command signal from the operating device (50a, 50b), generates an output signal to swing the swing post (7a, 7b), wherein the interference prevention controller (61F; 61FA) is constructed such that: the controller (61F; 61FA) defines, as an interference danger area, a differential angle range in which the left and right work fronts (A, B) are likely to come into contact with each other; the controller (61F; 61FA) defines, as a semi-interference danger area, a differential angle area adjacent to the interference danger area and in which the left and right work fronts (A, B), although kept free from contact under a stopped state thereof, are liable to come into contact when operated to make relative approaches; and when the differential angle (θc) between the left and right work fronts (A, B), calculated from the sensor signals sent from the swing post angle sensors (67a, 67b), is present in the semi-interference danger area and the work fronts (A, B) are operated to make relative approaches, the controller (61F; 61FA) outputs a signal to reduce the swinging speed of the swing post (7a, 7b). a lower travel structure with a travel device; an upper bodywork that is provided at an upper section of the lower travel structure and includes an operator cabin; left and right swing posts (7a, 7b) provided on front left and right sides of the upper bodywork such that the swing posts (7a, 7b) each swing in both leftward and rightward directions; left and right work fronts (A, B) provided on the left and right swing posts (7a, 7b) such that the work fronts (A, B) each sway vertically; operating devices (50a, 50b) which each give an operational instruction to the swing post (7a, 7b) and the work fronts (A, B); and swing post angle sensors (67a, 67b) which each sense a swinging angle of the left or right swing post (7a, 7b); the working machine characterized by comprising an interference prevention controller (61F; 61FA) which, pursuant to a differential angle (θc) between the left and right work fronts (A, B) that has been calculated from sensor signals sent from the swing post angle sensors (67a, 67b), and to a command signal from the operating device (50a, 50b), generates an output signal to swing the swing post (7a, 7b), wherein the interference prevention controller (61F; 61FA) is constructed such that: the controller (61F; 61FA) defines, as an interference danger area, a differential angle range in which the left and right work fronts (A, B) are likely to come into contact with each other; the controller (61F; 61FA) defines, as a semi-interference danger area, a differential angle area adjacent to the interference danger area and in which the left and right work fronts (A, B), although kept free from contact under a stopped state thereof, are liable to come into contact when operated to make relative approaches; and when the differential angle (θc) between the left and right work fronts (A, B), calculated from the sensor signals sent from the swing post angle sensors (67a, 67b), is present in the semi-interference danger area and the work fronts (A, B) are operated to make relative approaches, the controller (61F; 61FA) outputs a signal to reduce the swinging speed of the swing post (7a, 7b). the controller (61F; 61FA) defines, as an interference danger area, a differential angle range in which the left and right work fronts (A, B) are likely to come into contact with each other; the controller (61F; 61FA) defines, as a semi-interference danger area, a differential angle area adjacent to the interference danger area and in which the left and right work fronts (A, B), although kept free from contact under a stopped state thereof, are liable to come into contact when operated to make relative approaches; and when the differential angle (θc) between the left and right work fronts (A, B), calculated from the sensor signals sent from the swing post angle sensors (67a, 67b), is present in the semi-interference danger area and the work fronts (A, B) are operated to make relative approaches, the controller (61F; 61FA) outputs a signal to reduce the swinging speed of the swing post (7a, 7b).