A multistage column crystallizer is a column crystallizer partitioned with perforated plates. From the viewpoint of economy, multistage column crystallizers have been developed to overcome the redundancy of equipment due to the duplication of mixers and other hardware in a cascade of mixed-suspension, mixed-product-removal crystallizers. The aims of this study are to clarify the characteristics of the multistage column crystallizers and to control the calcium carbonate particle size. The staging effects of the column crystallizer on the particle size were experimentally investigated by the gas-liquid reaction crystallization of calcium carbonate in the three-stage column crystallizer. The particle size of calcium carbonate obtained by the multistage column crystallizer becomes larger than that obtained by the standard column crystallizer. The dominant particle size increases with a decreasing opening ratio of the perforated plate, whereas it decreases with increasing CO2 content in the gas, because the particles produced re-dissolve by the dissolution of CO2.