By employing a uniformly compact side-pumping system, a high-energy electro-optical Q-switched Nd:YAG ceramic laser has been demonstrated. With $420\mathrm{W}$ quasi-cw laser-diode-array pumping at $808\mathrm{nm}$ and a $100\mathrm{Hz}$ modulating repetition rate, $50\mathrm{mJ}$ output energy at $1064\mathrm{nm}$ was obtained with $10\mathrm{ns}$ pulse width, $5\mathrm{W}$ average output power, and $5\mathrm{MW}$ peak power. Its corresponding slope efficiency was 29.8%. The laser system operated quite stably and no saturation phenomena have been observed, which means higher output energy could be expected. Laser parameters between ceramic and single-crystal Nd:YAG lasers have been compared, and pulse characteristics of Nd:YAG ceramic with different repetition rate have been investigated in detail. The still-evolving Nd:YAG ceramics are potential super excellent media for high-energy laser applications.