In a method for mixing a small amount of a liquid sample with a second liquid, the liquid sample is first fed into a mixing vessel. Thereafter, the second liquid is discharged from an orifice of a second liquid pipette tip into the vessel, and the liquid sample and the second liquid are thereby stirred with each other. The small amount of the liquid sample is thus efficiently stirred by the second liquid and is thereby uniformly mixed with the second liquid. Also, the liquid sample and the second liquid are mixed with each other in an accurate mixing ratio.