To provide a manufacturing method of a rotary anode X-ray tube for easily and precisely measuring the rotary unbalance of a heavy rotary structure in a rotary anode having a dynamic pressure slide bearing in the atmosphere.

A rotor 20 of the rotary structure 58 is fitted to a fixed support tool 70 that has external dimensions that are nearly the same as those of a stator and allows a high-pressure fluid 72 to flow out of the inside instead of the columnar stator. While the high-pressure fluid 72 is allowed to flow to gaps 74a, 74b between the rotor 20 and the fixed support tool 70, the rotary structure 58 is rotated speedily by a stator 75, thus forming a static pressure slide bearing 74 between the rotor 20 and the fixed support tool 70 and measuring the rotary unbalance of the rotary structure 58.