An X-ray radiographing apparatus incudes a power assist device (10) for causing a driving mechanism to generate force for assisting that force which is added to a handle assembly (20) of a spot film device (3) in a direction, so that the spot film device (3) is moved by the sum of both forces in the direction. The movement of the handle assembly (20) is detected by a pressure sensor (21), so that the detecting signal responsive to the movement is outputted to a control circuit (22). A driving signal responsive to the detecting signal is supplied from the circuit (22) to the driving mechanism, so that the spot film device (3) is moved in the direction. A component of the weight of the handle assembly (20) is balanced with that of a counter weight (30), whereby the pressure sensor (21) is prevented from being wrongly operated by the component of the weight of the handle assembly (20). The width of blind zone of the pressure sensor (21) can be made narrower. The response speed of the spot film device (3) can be made narrower. The response speed of the spot film device (3) can be made higher and its stop accuracy can be enhanced. In addition, the starting force of the pressure sensor (21) can be made smaller. The burden of the operator can be more remarkably reduced. It may be designed that the rotational moment of the handle assembly (20) is balanced with that of the counter weight (30).
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