The Subaru adaptive optics system (AO188) is a 188-element curvature sensor adaptive optics system that is operated in both natural and laser guide star modes. AO188 is installed at Nasmyth platform of the 8m Subaru telescope as a facility AO system. The laser guide star mode for AO188 has been commissioned and offered for use in science operation since 2011. The performance of AO188 in the laser guide star mode has been well verified from on-sky data obtained with the infrared camera and spectrograph (IRCS). In this paper, we describe the operation procedure and observing efficiency for the laser guide star mode. We also show the result of the on-sky performance evaluation of AO188 in the laser guide star mode and the characterization of the laser guide star, together with the obtained science results.