  We present an X-ray spectral study of the prototype far-infrared galaxy
NGC6240 from ASCA. The soft X-ray spectrum (below 2 keV) shows clear signatures
of thermal emission well described with a multi-temperature optically-thin
plasma, which probably originates in a powerful starburst. Strong hard X-ray
emission is also detected with ASCA and its spectrum above 3 keV is extremely
flat with a prominent iron K line complex, very similar to that seen in the
Seyfert 2 galaxy NGC1068 but about an order of magnitude more luminous
[L(3-10keV)=1.4E42 erg/s]. The hard X-ray spectrum indicates that only
reflected X-rays of an active galactic nucleus (AGN) buried in a heavy
obscuration [N(H)>2E24 cm-2] are visible. This is evidence for an AGN in
NGC6240 emitting possibly at a quasar luminosity and suggests its significant
contribution to the far-infrared luminosity.
