To facilitate a maintenance and an inspection by simplifying a device.

This filtration device for a coolant is provided with a case 21 having a storage part 22 with an inlet 22a for the coolant 24 in its upper surface, and an erection part 23 erected upward from the storage part 22 and having a discharge port 23a in its upper end. The case 21 is provided with a scraper conveyer 25 carrying precipitated materials in the storage part 22 toward the discharge port 23a in its inside. A cylindrical filtration drum 35 having a filtration material 35a in its circumferential face is disposed in the storage part 22 positioned between the inlet 22a and the erection part 23 in parallel to an orbiting shaft center of the scraper conveyer 25 so as to be freely rotate. The upper part of the filtration drum 35 is exposed upward from an oil surface of the coolant 24 stored in the storage part 22, and a drum driving device 40 rotating the filtration drum 35 reversely to the orbiting direction of the scraper conveyer 25 is provided.