The size of bubbles distributed from a horizontal nozzle into shear field generated by a Couette flow between concentric cylinders was investigated using dual high-speed video cameras as parameters, i.e., shear rate, gas flow rate, nozzle diameter, gas chamber volume and liquid viscosity. When the bubble was lifted up by buoyancy and stretched horizontally by shear flow, the cut of the bubble neck was caused by the greater deformation. When the inclined bubble angle by shear flow was greater than the elevation angle by buoyancy, the bubble's detachment was governed not by viscosity but by shear flow. To estimate the bubble size, a correlation equation was proposed in this study.