Air- and CO₂-bubble plumes in stratification are studied by laboratory-scale experiments. These plume behavior is important in CO₂ ocean sequestration or destruction of stratification using bubble plume. The relations of the depth of intrusion to the strength of stratification, the flow rate of bubbles, and the diameter of bubbles are investigated by using non-dimensional numbers. The results indicate a new tendency that the larger the bubble size becomes, the shallower the depth of intrusion. Also, our numerical simulation method for two-phase flow is validated by comparing with the experiments.