The 2011 Tohoku tsunami caused severe damage to laver aquaculture in Tokyo Bay. We performed investigations at several fisheries cooperatives and organized spatial variations of damage degree for each of farming facilities. We then carried out numerical hindcasting of the tsunami to elucidate the damage mechanisms using an unstructured finite volume circulation model FVCOM. From the investigation and the numerical simulation results, the degree of damage was found to be correlated to the magnitude of the maximum drag stress on the facilities rather than the maximum tsunami height. We also made a prediction of tsunami damage to seaweed farming cased by each of expected earthquakes and found out that a Keicho-type earthquake may lead to heavier damage in the southern part of the bay.