Currently, in terms of the utilization of blue carbon, it is practically expected to be a powerful approach for achieving carbon neutrality. However, there is a challenge for crediting such seaweed beds when it comes to the development of a method to efficiently determine the area and existing amount of seaweed beds which are a source of CO₂ absorption. Moreover, within the shallow-water areas on which the seaweed beds are growing, there are plenty of dotted reefs and the currents in this area are often fast due to breaking waves. In this regard, an efficient method for monitoring the status of seaweed beds has not yet been fully established at present. On the premise of such circumstance, in recent years, the green laser bathymetry equipment to be carried on small aircraft has made it possible to obtain detailed topographic data in a short time in shallow-water areas that had been difficult to survey in the past. Additionally, there are specifically water surface, seaweed bed and seafloor for ALB in classification based on the difference in the reflection intensity of the irradiating laser. After multiplying the leaf length of seaweed beds by the distribution of seaweed beds in the aerial photograph, it is feasible to accurately calculate the abundance of seaweed beds. In the study, the information on the distribution of seaweed beds on a trial basis is acquired in trial with the help of point clouds acquired by ALB. Furthermore, the seafloor topography which is the foundation for the growth of seaweed beds is also obtained accordingly.