We study a warping instability of a geometrically thin, non-self-gravitating, circumbinary disk around young binary stars on an eccentric orbit.
Such a disk is subject to both the tidal torques due to a time-dependent binary potential and the torques due to radiation emitted from each star.
The tilt angle between the circumbinary disk plane and the binary orbital plane is assumed to be very small.
We find that there is a radius within/beyond which the circumbinary disk is unstable to radiation-driven warping, depending on the disk density and temperature gradient indices.
Since the tidal torques can suppress the warping in the inner part of the circumbinary disk, the disk starts to be warped in the outer part.
While the circumbinary disks are most likely to be subject to the radiation-driven warping on a AU to kilo-AU scale for binaries with young massive stars more luminous than 10^4 Lsun, the radiation driven warping does not work for those around young binaries with the luminosity comparable to the solar luminosity.