PURPOSE: To set a sample conveyance quantity equally to the content of a cell and to use a sample effectively by detecting a break of sample liquid in a feeding flow passage in front of the flow cell and removing entering air bubbles.
CONSTITUTION: A liquid feeding means 2 feeds the sample liquid 4 to the flow passage (a) by 0.4ml in 0.8 second from the start of feeding. Then a liquid feeding means control part 6 switches the speed of the means 2 and operates an air bubble detecting means 5. The sample liquid is fed by 0.1ml in one second from the switching. Then when the means 5 detects an air layer due to a liquid break, the means 2 is stopped according to the detection output and the means 2 is driven reversely. This reverse driving is carried out until the liquid 4 is fed backward in the flow passage (a) and the air-layer detection signal from the means 5 is ceased. Consequently, the air layer entered into the flow cell 3 is discharged from the cell 3, which is filled with the liquid 4.