The invention relates to an automatic sampler. The automatic sampler comprises a safety door with an opening and a sample rack having an operation part, the operation part is used for passing the sample rack through the opening of the safety door and inserting the sample rack into the inner part of the automatic sampler or taking out the sample rack from the automatic sampler, under states that the safety door is closed and the sample rack is in an inserting state, the internal part and the external part of the automatic sampler are separated, under state that the sample rack is in the complete inserting state, the safety door cannot move by relating to the automatic sampler.