We demonstrate a high-power 556nm yellow-green laser generated by intracavity frequency doubling of a diode side-pumped Nd:YAG laser at 1112nm. A symmetrical L-shaped flat-flat cavity was employed to implement efficient operation of the low-gain 1112nm transition and to achieve good power scalability. The coatings of the cavity mirrors were carefully designed to optimize the performance of the laser, and a 92W continuous wave laser output at 1112nm was achieved when the pumping power of the laser diodes reached 960W. By intracavity frequency doubling of the fundamental laser in a lithium triborate crystal, the maximum power of the frequency-doubled output at 556nm was found to be as high as 52.3W with a pulse repetition frequency of 10kHz. This corresponds to an optical-to-optical conversion efficiency of about 5.4%.