A filter includes a crucible, a filtering container, and a receiving tank. The crucible has a heater for heating a pre-filtered object to comprise a primary material in liquid and at least one other material in solid. The filtering container has a body, a sieve, and a press rod. The body connects with the crucible for receiving the heated pre-filtered object in a channel and provides a guide-out member; the sieve is disposed in said channel; and the press rod movably received in the channel for pressing the primary material of the pre-filtered object to flow through the sieve and to the guide-out member. The receiving tank has an entrance facing the guide-out member of the filtering container to receive the filtered primary material.