A dual-probe scanning near-field optical microscope was developed. The probe pair positioning was carried out using conventional microscopy with an accuracy beyond the diffraction limit. The distance dependence of the interprobe light transfer was measured to show the strong far-field influences. A dual-probe observation of an optical grating was performed. Gained two signals contained various information from the probe-pair and the sample. A method to process the two signals was suggested and discussed using three dimensional finite-difference time-domain simulations. Two independent signals specific to each probe were shown to be extracted by the procedure. © 2012 The Surface Science Society of Japan.