A laser diode partially end-pumped, electro-optically Q-switched, Yb:Y₃Al₅O₁₂ (Yb:YAG) slab laser was reported. We obtained output energy of 14.6 mJ/pulse with a pulse width of 30 ns at a repetition frequency of 2 kHz, and the corresponding peak power was 480 kW. The beam quality factors M² in the unstable direction and the stable direction was 1.32 and 1.25, respectively.