The invention discloses a metal dust filtering apparatus. The apparatus comprises a filter chamber, a metal dust concentration detector and a waste water treatment apparatus; the filter chamber is in U-type structure and is divided into a left cavity and a right cavity; the upper part of an outer wall at the left side of the left cavity is provided with a first air intake and a second air intake, the lower part of the outer wall at the left side of the filter chamber is provided with a controller, the top part of the left cavity is provided with a variable frequency motor, a rotating shaft is arranged on the variable frequency motor, and the inner part of the left cavity is provided with a first filter screen; the upper part of an outer wall at the right side of the right cavity is provided with a gas outlet, and the inner part of the right cavity is provided with a second filter screen; the bottom of the filter chamber is provided with a first base, a second base and a water outlet; and the waste water treatment apparatus and the water outlet are connected by a waste pipe, and the waste water treatment apparatus is also provided with a drain pipe. The metal dust filtering apparatus has the advantages of simple structure, good filtering effect, and good practicality.