We report a high-beam-quality diode-side-pumped Nd∶YAG intracavity-frequency-doubled laser. The thermal lensing effect of Nd∶YAG laser is compensated by using concave crystal rod. We have designed a convex-convex cavity based on the thermal focal length of the laser module to control the beam quality of the fundamental frequency laser. An acousto-optic Q-switching is used to modulate the fundamental frequency laser, and a type-II critical phase-matched lithium borate (LBO) crystal is used to generate frequency doubled laser. At a pump current of 21 A and a repetition frequency of 9 kHz, we obtain a 532 nm laser with an average power of 21.1 W and a pulse width of 60 ns. At maximum average power of the 532 nm laser, the beam quality has been measured to be M_x²×M_y²=1.33×1.36, and the power stability fluctuation within 1 hour is less than 3%.