An autofocus apparatus according to an embodiment of the present invention is provided with an image acquirer, a pattern controller, and a focus controller. The image acquirer includes an optical system which forms an image of an object at a predetermined magnification and an image capturer which photographs the image of the object formed by the optical system. The pattern controller includes a generator which generates a pattern in a size according to the predetermined magnification of the optical system and a projector which projects the pattern generated by the generator onto the object. In the focus controller, an image of the projected pattern formed by the optical system at the predetermined magnification controls a focus position of the optical system based on the image of the object photographed by the image capturer.