The energy spectra of X-rays produced by an LiTaO3 single crystal have been measured at the pressures of 8 × 10−4−4 Pa. The energy spectra showed that the endpoint energy steadily increased with decrease of pressure at 2–4 Pa and gradually decreased with decrease of pressure at 0.1–2 Pa, and became almost constant below 0.1 Pa. The amount of X-rays steadily increased with decrease of pressure at 2–4 Pa and almost saturated below 0.5 Pa. The change of X-rays produced by the LiTaO3 single crystal was compared with the previous works and discussed in relation to the distance between the crystal surface and the target.