To provide a device for detecting the degradation of a lubricant having a high flexibility of arrangement in the internal of a bearing or the like, and high stability and accuracy, while including a detection section enabling the easy charge or discharge of a lubricant and the reduction in size thereof, and also to provide a bearing provided with the device for detecting the degradation of a lubricant.

The device 1 for detecting the degradation of a lubricant includes: two optical fibers having the tops arranged in parallel to each other via a space 10 for the arrangement of the lubricant 6; a light emitting element 2 disposed in the base end of one optical fiber 4 and a light reception element 3 disposed in the base end of the other optical fiber 5; and determination means 7 for determining the amount of foreign matters mixed with the lubricant 6, based on output from the light reception element 3. Both of the optical fibers 4 and 5 are covered with an optical fiber fixing member 11 to be mutually fixed. The optical fiber fixing member 11 is provided with a groove 12 extending from the top end side of the optical fibers toward the base end side, so that the space 10 between the two optical fibers is exposed.