The estimation of accurate cutting time before cutting is important for improving productivity. Estimation of cutting time calculated by "length of tool path / command feedrate" can easily be obtained in commercial CAM systems because NC programs contain machining information, such as tool positions, feedrate, etc. However, the actual cutting time is longer than cutting time calculated by "length of tool path / command feedrate" due to acceleration and deceleration which occurs along the tool path. In this study, an estimation system of accurate cutting time based on the control system of the machine tool is proposed. Experiments were conducted to cut complex shapes using the NC machine tool to compare the actual cutting time, estimated cutting time of commercial CAM systems and those of the proposed system. The estimation error of the proposed system was only 2 %, while the estimation error of a commercial CAM system was 51 %.