A fluid delivery method for delivering a liquid sample to a flow cell including a taper section including a first and a second inner walls opposing the first inner wall, which is inclined to the second inner wall so that a distance between the first and the second inner walls at a downstream side of the taper section is shorter than a distance at an upstream side of the taper section, and including measurement flow path provided downstream of the taper section, through which a liquid sample flows together with a sheath fluid. The fluid delivery method includes sample introduction of delivering the liquid sample into the taper section along the second inner wall until the liquid sample reaches the measurement flow path, and sample pressing by delivering the sheath fluid into the taper section along the first inner wall after the liquid sample reaches the measurement flow path.