An auto-focus apparatus, a focus adjusting method, an image capturing apparatus and an image capturing method make it possible to perform accurate focus adjustment on a subject for which the focus should be adjusted. The auto-focus apparatus emits an irradiation wave from emitting means for irradiation to a subject while changing an incident angle of the irradiation wave, detects an incident angle of a reflected wave of the irradiation wave reflected by the subject, incident on light receiving means positioned corresponding to the emitting means, determines based on the emitting angle and the incident angle whether or not the subject is a subject for which the focus is adjusted, and adjusts the focus on the subject when determining that the subject is the subject for which the focus should be adjusted, thereby making it possible to accurately adjust the focus on the subject for which the focus should be adjusted.