To provide a device of a diagnosing foreign substances in a lubricant for simply and rapidly diagnosing the foreign matter in the lubricant, and to provide a method of diagnosing the foreign substances in the lubricant.

The device of diagnosing the foreign substance in the lubricant has an injection cylinder 15, constituted of an outer cylinder 13, filled with the lubricant 11 and having a warming part 12 for keeping the warmth of the inside of the outer cylinder or internally warming it, and an inner cylinder 14 for pressing the warmed lubricant 11 under a predetermined pressure; and a filter part 16 for keeping the leading end part of the injection cylinder 15 equipped with a filter 16a, and is constituted so that the inner cylinder 14 is pressed under a predetermined pressure to collect the foreign matter 17 in the lubricant 11 by the filter part 16.