Recently, local probes used in optical experiments added a new dimension to the study of the optical properties of small particles lying on a surface. Until now, several theoretical frameworks, developed to understand the interaction of optical fields with mesoscopic and nanoscopic objects, emphasized mainly the prediction of the electric near-field distributions generated by these structures. This paper demonstrates how such subwavelength dielectric surface structures also produce a particular confinement of the optical magnetic near field when the sample is illuminated by a surface wave.