Abstract: Sample cups containing serum are removably loaded in a plurality of annular holders flexibly connected to make up a slidable chain which is moved through a limited path and passes a sampling position. Ion-selecting electrodes and a reference electrode are slightly spaced from the sampling position. A predetermined amount of serum in the sample cup that has arrived at the sampling position is distributed to a measurement tank. The electromotive force based on the ion to be measured is detected, and the ion concentration is printed out on a printer on the basis of the detection result. Normally, samples sequentially arriving at the sampling position are distributed to the measurement tank for continual analysis. Upon receipt of an emergency sample, an interruption switch on the operation panel is depressed for transmitting an interruption measurement command to a control section.