Abstract: A rotational-part supporter has a structure in which one of either an inner part or an outer part is fixed, and the other one is rotated, and a main rotational shaft lies between the inner and outer parts. A revolving speed below a revolving speed based on a lubrication lifetime predicted for each rotational bearing (3) is stored in a memory (61) disposed in the lubricant supply controller (6). When a revolving speed obtained by actual rotation coincides with the stored revolving speed in the rotational bearing (3) after supplying the lubricant, the controller (6) issues a signal indicating that the lubricant should be newly supplied, and thereby a safety operation can be realized.