In order to evaluate applicability of rock cut-slope investigation system, typical clinometer and photogrammetry investigation system were used for rock slopes; first for 7 discontinuities, and secondly, 10 discontinuities, and the results were compared. The first verification was performed depending on discontinuity joint shapes and slope angles, and the second verification was performed depending on shot time and shot locations. The results showed that differences of dip direction $1^{circ}{sim}4^{circ}$, dip $0^{circ}{sim}4^{circ}$. In the second verification test, the differences of dip direction was $0^{circ}{sim}6^{circ}$, and dip $0^{circ}{sim}6^{circ}$. The photogrammetry method for rock slope survey system is quite reliable when clinometer generally shows ${pm}10^{circ}$ errors due to surface roughness and investigator.