The dispersion of batch time, i.e., the time for finalizing batch crystallization satisfying batch end conditions, in internally seeded cooling crystallization with direct nucleation control (DNC) was estimated by computer simulation. The batch time is considered to disperse at such crystallization due to stochastic nucleation. In this study, first, a population balance equation was digitized for numerical calculation, and the simulation was developed in MATLAB. Then, repetitive simulations of internally seeded cooling crystallization considering stochastic nucleation with DNC were performed. Finally, the batch time of each simulation was arranged. As a result, it was found that there is little batch time dispersion in crystallization controlled by DNC and without adding seed.