An autofocusing apparatus suitable for use in a photographic printer is provided. The printer permits mounting of plural carriers for holding original films of different sizes thereon respectively and is capable of setting a focusing position on the basis of an AF curve determined when a reference carrier out of a plurality of carriers is mounted. The apparatus is also so constructed that the AF curve is compensated based on differences between the position of the original film upon mounting of the reference carrier and that of the original film upon mounting another carrier. Accordingly, an original film can be positioned at its optimal focusing position regardless of which of the plurality of carriers is used.