A method for controlling a hazardous element in an encapsulating resin of a resin encapsulation semiconductor device includes subjecting the device to qualitative analysis with a fluorescent X-ray analyzer to judge whether the hazardous element is contained in the encapsulating resin, aligning a plurality of devices with each of upper and lower surfaces of the devices brought into a plane, setting the surfaces of the devices to cover a full X-ray irradiation plane and subjecting the devices to quantitative analysis with the fluorescent X-ray analyzer to obtain an analytical value of the hazardous element in the encapsulating resin for upper and lower surfaces of the devices, and judging whether the analytical value of the hazardous element which is less influenced by a coexistent element of the analytical values for the upper and lower surfaces of the devices exceeds a threshold value.