A laser-induced breakdown spectroscopy (LIBS) system based on a hollow optical fiber was developed. The fiber is used for both the delivery of the excitation laser and detection of emission spectra. The fiber probe enables the measurement of unexposed sample surfaces by inserting or stabbing the probe into a sample. The feasibility of the LIBS system was evaluated by measuring soil salinity. The measurement sensitivity was improved by introducing argon onto the sample surface through the bore of the hollow fiber, and the lowest detectable limit for the NaCl contained in a soil sample was 0.01 wt %.