A device for separating tramp metals from liquid raw materials, comprising: a body unit including a tank having an open top side, a close bottom side, an inlet, and an outlet, the tank further defining a first space so that the liquid raw materials can be introduced from the inlet, passed through the first space and flowed out from the outlet; a holding unit including a cover with a plurality of holes and a plurality of non-magnetic holders, the cover secured on the open top side of the tank and having an upper surface and a lower surface, each of the non-magnetic holders having a holding body and an opening disposed on one end of the holding body, the non-magnetic holders disposed on the lower surface of the cover in a spaced manner and in a way that each of the openings thereof corresponds to each of the holes of the cover and the holding bodies thereof are received in the first space of the tank; a magnetic unit including a base with an upper side and a lower side, a plurality of magnet members mounted on the lower side of the base in a spaced manner and an enclosure having a telescopic wall, a second space defined by the telescopic wall, an upper end connected to the lower side of the base and a lower end connected to the upper surface of the cover, the magnetic unit coupled to the tank in such a way that can move back and forth between a first and a second position, when the magnetic unit is located at the first position, the telescopic wall of the enclosure is in a compressed state and each of the magnetic members inserts into the holding body of each of the non-magnetic holders through the opening thereof and when the magnetic unit is located at the second position, the telescopic wall of the enclosure is in an extended state so that the magnet members are received in the second space thereof; a rinsing unit including an injector fixed on the inner surface of the tank for introducing a rinsing liquid from outside to the injector to rinse the non-magnetic holders for removing the tramp metals attracted on the surface of each of the non-magnetic holders when the magnetic unit is located at the second position; and a driving unit coupled respectively to the tank and the magnetic unit for driving the magnet unit to move back and forth between the first and second positions relative to the tank. a body unit including a tank having an open top side, a close bottom side, an inlet, and an outlet, the tank further defining a first space so that the liquid raw materials can be introduced from the inlet, passed through the first space and flowed out from the outlet; a holding unit including a cover with a plurality of holes and a plurality of non-magnetic holders, the cover secured on the open top side of the tank and having an upper surface and a lower surface, each of the non-magnetic holders having a holding body and an opening disposed on one end of the holding body, the non-magnetic holders disposed on the lower surface of the cover in a spaced manner and in a way that each of the openings thereof corresponds to each of the holes of the cover and the holding bodies thereof are received in the first space of the tank; a magnetic unit including a base with an upper side and a lower side, a plurality of magnet members mounted on the lower side of the base in a spaced manner and an enclosure having a telescopic wall, a second space defined by the telescopic wall, an upper end connected to the lower side of the base and a lower end connected to the upper surface of the cover, the magnetic unit coupled to the tank in such a way that can move back and forth between a first and a second position, when the magnetic unit is located at the first position, the telescopic wall of the enclosure is in a compressed state and each of the magnetic members inserts into the holding body of each of the non-magnetic holders through the opening thereof and when the magnetic unit is located at the second position, the telescopic wall of the enclosure is in an extended state so that the magnet members are received in the second space thereof; a rinsing unit including an injector fixed on the inner surface of the tank for introducing a rinsing liquid from outside to the injector to rinse the non-magnetic holders for removing the tramp metals attracted on the surface of each of the non-magnetic holders when the magnetic unit is located at the second position; and a driving unit coupled respectively to the tank and the magnetic unit for driving the magnet unit to move back and forth between the first and second positions relative to the tank.