Ion extraction from a plasma plays important roles in various technology fields, such as ion plantation, ion beam generation, and laser isotope separation. In this paper, the behavior of ions during the extraction process is investigated in detail using two types of particle simulation codes, and the ion‐extraction time is compared with the results of an analytical model. A two‐dimensional code, in which the electrons are assumed to be distributed, in accordance with the Boltzmann relation, while the ion behavior is calculated by the particle model, results in essentially the same values for ion‐extraction time, as with the analytical model. On the other hand, the results of the one‐dimensional full particle code partly differ from that of the two‐dimensional code and the analytical model. The use of the Boltzmann distribution of the electrons tends to overestimate the ion‐extraction time up to a factor of approximately 2 at its worst point.