PURPOSE: To secure the safety of a worker by way of preventing leakage of an X-ray by preventing formation of a clearance on an X-ray leakage preventive member suspended to surround the circumference of a x-ray passing position.

CONSTITUTION: An X-ray radiated from an X-ray generating means 6 passes a passage 8a of a protective pipe 8 and a passage 11a of a clamper 11, transmits a printed board 4, passes a transmission hole 1a of a work table 1 and reaches an X-ray camera 2. The clamper 11 is provided on the protective pipe 8 free to vertically move, and the printed board 4 is positioned. An X-ray leakage preventive member 19 is suspended to surround the clamper 11. The X-ray leakage preventive member 19 is constituted by suspending two pieces of metal contained sheets 19a with an interval in parallel and suspending two rows of fine chains 19b within this interval. The chains 19b are made of a material capable of absorbing an X-ray, suspended vertically not to make a clearance and prevents leakage of the X-ray.