To provide an aspiration unit capable of spraying liquid medicine and the like in a uniform predetermined particle diameter.

The aspiration unit comprises a fine-grained generating nozzle 12, a discriminating container 10, a discharge part 28, a particle-diameter setting means, a particle-diameter detecting means and a gas pressure control means. The fine-grained generating nozzle 12 crushes liquid medicine in fine-grained particles by a gas to generate fine-grained particles in the liquid medicine. The discriminating container 10 discriminates the fine-grained particles generated by the fine-grained generating nozzle. The discharge part 28 discharges ultra fine-grained particles discriminated from the fine-grained particles in the discriminating container only at an aspiration time. The particle-diameter setting means sets up the diameter of the ultra fine-grained particles. The particle-diameter detection means detects the particle diameter of the ultra fine-grained particles discharged from the discharged part. The gas pressure control means controls the pressure of the gas supplied to the fine-grained particle generating nozzle such that the particle diameter of the ultra fine-grained particles detected by the particle-diameter detecting means becomes the particle diameter of the ultra fine-grained particles.