Currently, near-field scanning optical microscopy offers a spatial resolution down to 10−30 nm. High resolution imaging spectroscopy enables us to visualize the exciton wavefunctions confined in semiconductor quantum structures. In this article, the principle of near-field optical wavefunction mapping is described. Then as an application, we performed mapping out of exciton and biexciton wavefunctions in single GaAs quantum dots. Significant displacement of the center of emission profiles was found, in contrast to the usual difference in the emission profiles of an exciton and a biexciton. By conducting a numerical calculation, such a displacement could be reproduced by introducing a shallow potential dip, which causes a significant difference in the penetration of the wavefunctions into the barrier. Precise mapping of exciton and biexciton wavefunctions of quantum-confined structures will provide a good probe for weakly localized states due to local strain and disorder.