An inter-cell hard hand-off timing determining method performs inter-cell hard hand-off by clearly determining a hand-off timing with a software method without assistance of hardware, thereby smoothly enabling traffic in a small base station that is installed in a shadow region or low traffic regions and reducing undesirable addition for hardware in increasing the small base station. The method is performed by the following steps of: identifying whether a mobile station has moved to a small base station; when it is determined that the mobile station has moved to the small base station, asking a selector and vocoder processing execution to report a power measurement report message having pilot signal strengths of an active set; reporting the PMRM to a call control execution; and when the mobile station is positioned at a boundary of a general base station, performing a inter-cell hard hand-off.