The authors have studied the automation of exterior wall sealing work in order to secure stable quality and achieve safety of work at high altitudes. The automation system is divided into two functions: operating and supporting. The operating function consists of four subsystems including cleaning, primer coating, insertion of back-up material, and filling with sealant. The supporting function consists of two subsystems, moving and sensing. This report describes the study results of two of the above subsystems: filling with sealant and sensing. For the filling with sealant subsystem, 2 parts silicone sealant is used. The base compound and curing agent for the 2 parts silicon sealant are mixed at the specified proportion and discharged. This subsystem consists of two types of pneumatic pumps, a measuring cylinder, and a static mixer. The test results show that both the mixing proportion and discharge were in the allowable range. The sensing subsystem measures the positions and width of joints by using an ultrasonic sensor. Although the sensing accuracy varied depending on the relationship among distance between the sensor and the wall surface, moving speed of the sensor, and the joint width, it was found that the sensing subsystem could be used without problems under presumable actual conditions. Exterior sealing work can be automated only when all the aforementioned subsystems are established. However, the study confirmed that the filling with sealant subsystem and the sensing subsystem were fully effective elements of the technology.