The fine particles of organic compound have been prepared using supercritical carbon dioxide as an anti-solvent and the effects of various experimental variables on the particle size and their morphology were also investigated. We selected benzoic acid as a testing material and used methanol to dissolve benzoic acid. It can be said that there are several processes depending on the method to inject supercritical fluid or solution. In this work three different kinds of methods, which are (1) addition of supercritical fluid in the solution of constant volume, (2) method to inject solution into supercritical fluid and (3) continuous co-current spraying of solution and supercritical fluid, have been utilized. And the fine particles have been produced varying processing methods as well as experimental variables and the effects of those on the particle characteristics have been analyzed. In the case of injecting supercritical fluid into the constant-volume solution like method (1) we have performed experiments changing crystallizer pressure, capillary diameter and injection time of anti-solvent. The experiments show that particle size are proportional to the capillary diameter and the anti-solvent injection time, whereas particle sizes decrease with increasing crystallizer pressure. In the experimental method (2) we can get the results such that the particle sizes decrease with increasing crystallizer pressure but increase with increasing crystallizer temperature and capillary diameter. The experimental method (3), which sprays anti-solvent and solution co-currently, is the most reliable method to produce fine particles and the results show that particle sizes increase with increasing crystallizer temperature, capillary diameter and retention length contrary to the opposite behaviors of crystallizer pressure, capillary length, solution concentration and CO₂ vent rate. From the data for each experimental methods and conditions we have been able to explain the general behaviors of particles size change by employing supersaturation ratio and supersaturation rate consistently.