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Crosswell seismic data were acquired in three sections crossing a tunnel of 3 different types; one was empty,another was filled by sand, and the other was filled by rock debris. Both the P- and S-wave first arrivals were pickedand the traveltime tomography was conducted to generate the P- and S- wave velocity tomograms on the all three sections.Among six tomograms, only one tomogram shows a low velocity zone that can be interpreted as a tunnel image. Thetomogram is the P wave velocity image of a section that crosses an empty tunnel. The result of numerical analysis forthe spatial resolution of the traveltime tomography was consistent to this finding.