  We report the discovery of X-ray emission at the position of the old
classical nova DK Lacertae using the Swift satellite. Three observations were
conducted using the X-ray telescope 62 years after the discovery of the nova,
yielding 46 source signals in an exposure time of 4.8 ks. A
background-subtracted count rate was 9+/-2x10^{-3} counts s^{-1}, corresponding
to a detection significance level of 5-sigma. The X-ray spectrum was
characterized by a continuum extending up to about 7 keV, which can be modeled
by a power-law component with a photon index of 1.4--5.6, or by a thermal
bremsstrahlung component with a temperature of 0.7--13.3 keV, convolved with
interstellar absorption with an equivalent hydrogen column density of
0.3--2.4x10^{22} cm^{-2}. Assuming a distance of 3900 pc to the source, the
luminosity was 10^{32}--10^{34} ergs s^{-1} in the 0.3--10 keV energy band. The
origin of X-rays is considered to be either mass accretion on the white dwarf
or adiabatic shocks in nova ejecta, with the former appearing much more likely.
In either case, DK Lacertae represents a rare addition to the exclusive club of
X-ray emitting old novae.
