A range finder adapted for finding the object distance of a subject having a specific height includes a shell unit, an objective lens assembly, a magnifying unit having multiple selectable magnification ratios, and a range finding unit. The range finding unit includes a scale, a pointer, and a mark. The object distance of the subject is known by comparing the scale and the pointer in an imaging plane when an end of an image of the specific height of the subject formed on the imaging plane is aligned with the mark.