The concept of a MSMPR crystallizer, in which all crystals are assumed to disperse perfectly in suspension regardless of the crystal size, has mostly been used in the study on crystallization in order to simplify the discussion. However, there is a possibility that the spacial suspension density distribution in a crystallizer affects the crystal size distribution of the product. In this work, the effect of the spatial suspension density distribution in the crystallizer on the crystal size distribution of the product has been studied experimentally by using two types of continuous crystallizers. For expressing the mixing degree of all crystals of all sizes in the crystallizer, the multi-component mixedness defined by Ogawa was used after the definition was expanded. Experimental results show that the suspension density and the crystal size distribution are different at different heights in the crystallizers. The variation of the mixedness with impeller rotational speed is made clear. It is clarified that the mean crystal size of product crystals increases with decreasing mixedness. The usefulness of mixedness as an indicator of the classification in the crystallizer is made clear.