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The effects of growth interruption on the formation of InAs quantum dots (QDs) grown on GaAs substrates by molecular beam epitaxy were investigated. The growth interruption was carried out during the growth of InAs with a nominal thickness of 1.2 monolayers (ML). The number of growth interruptions was varied between 1 and 6, and the interruption time (t INT ) was varied between 5 and 15 s. After the growth interruption, a 2.8-ML-thick InAs was grown, and the total thickness was nominally 4 ML. The structural characterization was performed using an atomic force microscope. In the case of the growth with t INT ¼ 5 s, the average size of QDs decreased and their density increased with increasing number of growth interruptions. On the other hand, the size of QDs increased and their density decreased with increasing number of growth interruptions for the growth with t INT ¼ 10 or 15 s. These results suggested that the extremely uniform distribution of In adatoms in the wetting layer due to the migration of In atoms on the surface as well as the reduction of stress in the wetting layer due to the interchange of In and Ga atoms during the growth interruption affect the size and density of QDs.