A display apparatus to be inspected includes: a display panel in which pixel groups are arranged; and an optical element for providing image display for N viewpoints (N is a natural number more than one) from the pixel groups. An inspection apparatus includes: a image output device for outputting a test pattern including image signals different in the respective viewpoints to the display apparatus; and an extraction device for extracting the slope and the position of a boundary line segment in an inspection image displayed on the display apparatus. The extraction device detects positional accuracy between the display panel and the optical element on the basis of the slope and the position extracted by the extraction device.