To easily detect a defect of an internal component such as a diaphragm.

After starting defect detection processing, the diaphragm 12 is driven to intercept light taken in by a lens 11. Brightness of an image obtained based on output from an imaging device 13 after the diaphragm 12 is driven is detected. Based on the detected brightness, it is determined whether the diaphragm 12 breaks down. When the brightness of the image is 0 (pitch-dark), it is determined that the diaphragm 12 is driven normally, and when predetermined light quantity of a value other than 0 is detected, it is determined that the diaphragm 12 breaks down. The invention is applied to an imaging apparatus such as a digital video camera and a digital still camera.