A defect inspection apparatus which includes a pattern image obtaining unit obtaining a pattern image of a predetermined part by causing focusing control to be performed in order to achieve focus on the predetermined part within an observation object according to set focusing control parameters, a pattern image storing unit storing the pattern image, and a detecting unit detecting the presence/absence of an abnormal condition of a part to be inspected by making a comparison between the pattern image of a reference part within the observation object, and the pattern image of the part to be inspected within the observation object. The focusing control parameters, set when the pattern image of the part to be inspected is obtained, are determined based on sample information obtained when the pattern image of the reference part is obtained.