The digital dust indicator (Sibata P-5), one of the direct-reading instruments was evaluated for the respirable dust in the underground coal mine environments. As a reference, respirable dust was determined using three cyclones and/or impactors. All the tests were performed on aerosol in twenty underground coal mines. The coefficients of mass-relative concentration were 0.067+/-0.054 (Mean+/-Standard deviation) (range: 0.006-0.172). The relationship between relative concentration and temperature was not significant statistically. Also, the relationship of relative concentration and relative humidity was not significant. Mass concentration and relative concentration were 5.31+/-5.22 mg/m3 and 162+/-163 CPM (Mean+/-Standard deviation) respectively. The range of mass concentration was 1.22-22.69 mg/m3; relative concentration 16-628 CPM. The relationship of mass concentration and relative concentration was not significant in these ranges.