A suction device capable of spraying a liquid medicine or the like so that the particles have a set uniform diameter. It comprises a fine particle generating nozzle for generating fine particles of liquid medicine by pulverizing the liquid medicine by a gas, a separating vessel for separating the fine particles generated by the fine particle generating nozzle, a delivery section for delivering, only during suction, the superfine particles separated from the fine particles in the separating vessel, a particle size setting section for setting the particle size of the superfine particles delivered from the delivery section, a particle size detecting section for detecting the particle size of the superfine particles delivered from the delivery section, and a gas pressure control device for controlling the pressure of the gas fed to the fine particle generating nozzle so that the particle size of the superfine particles detected by the particle size detecting section may be equal to the particle size of the superfine particles set by the particle size setting section.