We experimentally investigated simultaneous microfluidic control and visualization of a heated region using gold nanoisland/VO₂ thin films. By focusing a laser on the film, we photothermally generated an air microbubble in nondegassed water. After the bubble generation, another laser spot was irradiated 48  μm away from the bubble center. As a result, a sudden onset of the rotational Marangoni flow was observed at 130 ms after the laser was turned on. At the same time, the heated region above 70°C was visualized based on the thermochromic property of the thin film. The heated area did not vary significantly at the onset of the flow, indicating that there is a threshold temperature or temperature gradient on the bubble surface for generating the rotational Marangoni flow. To understand the flow generation, we decreased the distance between the bubble and the laser spot. The resulting visualized heated region suggests that a part of the bubble surface has to be heated above 70°C to generate the rotational flow. In addition, the heated area during the flow generation remained small as the distance decreased. The gold nanoisland/VO₂ thin film is suitable for understanding and optimizing the rapid Marangoni flow generation.