A dissolver which is a device for dissolving spent fuel is composed of one slab and two barrels (stainless steel 310s). The fuel basket (stainless steel 304L) installed in the barrel is a device for taking out of the insoluble fuel cladding from the dissolver. The inside of the dissolver become high corrosive environment because dissolution is carried out under high temperature and high acid concentration. We developed the remote handling maintenance device and carried out the periodical thickness measurement of the dissolver because corrosion failure has occurred in the past. On the other hand, the thickness measurement of the fuel basket was carried out only once by destructive measurement at the time of renewal. Understanding of the corrosion tendency of the fuel basket and establishing of the non-destructive measurement method by remote handling are required. Therefore, we examined the method of thickness measurement of the fuel basket and established it.