Ball bearing and main shaft device for machine tool

A ball bearing comprising:

• an inner ring with an inner ring raceway groove on an outer circumferential surface;
• an outer ring with an outer ring raceway groove on an inner circumferential surface;
• a plurality of balls which are arranged in a rollable manner between the inner ring raceway groove and the outer ring raceway groove;
• and
• a retainer with a plurality of pockets for retaining the plurality of respective balls, wherein:
• the outer ring includes a plurality of radial holes which penetrate from the outer circumferential surface to the inner circumferential surface in the radial direction to supply lubricating oil, such that the ball bearing is lubricated by the lubricating oil;
• when inner diameter side opening portions of the plurality of radial holes are projected on an outer circumferential surface of the retainer along extension lines of central lines of the radial holes, at least parts of the projected inner diameter side opening portions are positioned within an area of two circles formed by connecting each of axial end portions of respective pockets of the retainer in a rotational axial direction of the ball bearing;
• and
• when the central line of any one radial hole among the plurality of radial holes coincides with a circumferential phase of a center of the ball, any other radial hole is formed such that when the inner diameter side opening portion of the radial hole is projected on the outer circumferential surface of the retainer along the extension line of the central line of the radial hole, at least parts of the projected inner diameter side opening portion overlap with an inner circumferential surface of the pockets when viewed from a radial direction of the ball bearing, and the central line of the other radial hole is separated from the circumferential phase of the center of the ball.