  We present results of optical-UV observations of the 200 Myr old
rotation-powered radio pulsar J0108$-$1431 with the Hubble Space Telescope. We
found a putative candidate for the far-UV (FUV) pulsar counterpart, with the
flux density $f_\nu = 9.0\pm 3.2$ nJy at $\lambda = 1528$ \AA. The pulsar was
not detected, however, at longer wavelengths, with $3\sigma$ upper limits of
52, 37, and 87 nJy at $\lambda =$ 4326, 3355, and 2366 \AA, respectively.
Assuming that the pulsar counterpart was indeed detected in FUV, and the
previously reported marginal $U$ and $B$ detections with the Very Large
Telescope were real, the optical-UV spectrum of the pulsar can be described by
a power-law model with a nearly flat $f_\nu$ spectrum. Similar to younger
pulsars detected in the optical, the slope of the nonthermal spectrum steepens
in the X-ray range. The pulsar's luminosity in the 1500--6000 \AA wavelength
range, $L \sim 1.2\times 10^{27} (d/210\,{\rm pc})^2$ erg s$^{-1}$, corresponds
to a high efficiency of conversion of pulsar rotation energy loss rate $\dot
{E}$ to the optical-UV radiation, $\eta = L/\dot{E} \sim (1$--$6)\times
10^{-4}$, depending on somewhat uncertain values of distance and spectral
slope. The brightness temperature of the bulk neutron star surface does not
exceed 59,000 K ($3\sigma$ upper bound), as seen by a distant observer. If we
assume that the FUV flux is dominated by a thermal component, then the surface
temperature can be in the range of 27,000--55,000 K, requiring a heating
mechanism to operate in old neutron stars.
