Waste coolant recycling method

To provide a waste coolant recycling method which can produce reusable coolant by removing silicon waste chips from waste coolant. The coolant recycling method 1a includes centrifugal circulation process (A) which comprises centrifugal process S2 for supplying a part of waste coolant 3 to centrifuge unit 2 having a stand-type centrifuge to separate centrifuged liquid 19 from solid content 17 and centrifuged liquid mixing process S3 for mixing centrifuged liquid 19 with waste coolant 3, membrane filtrating circulation process (B) which comprises membrane separation process S4 for supplying the rest part of waste coolant 3 to membrane separation unit 7 having a membrane filter 6 to separate concentrated liquid 22 from filtered liquid 21 and concentrated liquid mixing process S5 for mixing concentrated liquid 22 with waste coolant 3, and coolant mixing produce process S6 for mixing centrifuged liquid 19 after circulation with filtered liquid 21 to produce reusable coolant 4.