Large numbers of human induced pluripotent stem cells (hiPSCs) are required for making stable cell bank. Although suspension culture yields high cell numbers, there remain unresolved challenges for obtaining high-density of hiPSCs because large size aggregates exhibit low growth rates. Here, we established a simple method for hiPSC aggregate break-up using botulinum hemagglutinin (HA), which specifically bound with E-cadherin and disrupted cell-cell connections in hiPSC aggregates. HA showed temporary activity for disrupting the E-cadherin-mediated cell-cell connections to facilitate the break-up of aggregates into small sizes only 9hr after HA addition. The transportation of HA into the aggregates was mediated by transcellular and paracellular way after HA addition to the culture medium. hiPSC aggregates broken up by HA showed a higher number of live cells, higher cell density, and higher expansion fold compared to those of aggregates dissociated with enzymatic digestion. Moreover, a maximum cell density of 4.5 +/- 0.2x10(6) cellsml(-1) was obtained by aggregate break-up into small ones, which was three times higher than that with the conventional culture without aggregate break-up. Therefore, the temporary activity of HA for disrupting E-cadherin-mediated cell-cell connection was key to establishing a simple in situ method for hiPSC aggregate break-up in bioreactors, leading to high cell density in suspension culture.