There is disclosed a method of inspecting the outer wall of a honeycomb structure body which can be performed without relying on human sensory functions and in which a defect detection level and an inspection time per honeycomb structure body are constant, so that stable inspection can be performed. In a method of inspecting the outer wall of a honeycomb structure body 1 made of a ceramic material, while rotating the honeycomb structure body 1, the outer wall of the honeycomb structure body 1 is imaged by a line camera 2, and the thus obtained image is processed to judge whether or not a defect is present in the outer wall of the honeycomb structure body 1.