We have developed a 1 kHz regenerative amplifier using an Yb:Y(2)O(3) ceramic thin disk as the gain medium. Furthermore, the thermal conductivity and heat generation property of Yb:Y(2)O(3) ceramic were investigated. In the developed regenerative amplifier, a laser beam is bounced off the thin disk six times in each round trip. The output energy is over 2 mJ, spectral bandwidth is 1.8 nm at FWHM, and pulse duration after pulse compression is 0.9 ps.