To provide a method for evaluating the deterioration of a sealing material between exterior walls at an external joint part for a building in early stage when the abnormality is not recognized by a visual inspection, and further to provide an information by which a remaining life of the urethane-based sealing material can be estimated, and which is important in forming a maintenance program of the building.

The method for evaluating the deterioration of the urethane-based sealing material involves measuring an elution amount of an urethane component of the sealing material, and an amount of a plasticizer.