An autosampler consists of a needle to draw specimen from a specimen container into a passage therein; a block having a passage that follows the passge in the needle; a suction mechanism for drawing in the specimen by suction through the passages in the needle and the block; a discharge mechanism for discarding the specimen drawn in by the suction mechanism; and a detecting device for detecting air bubble in the specimen, the detecting device being embedded in the block in such a manner as to face the passage in the block. The detecting device detects the air bubbles in the specimen according to changes in physical or chemical properties of the specimen passing through the passage in the block. The discharge mechanism is activated by the detecting device to discharge air-mixed specimen. When even a small amount of air is drawn into the passage from the specimen container, in which only a small amount of specimen is contained, the air specimen can reliably be distinguished from normal specimen by this autosampler. Therefore the reliability of the system using the autosampler can be significantly improved.