  We report photometric and spectroscopic observations of the nearby Type Ia
Supernova (SN Ia) 2012ht from $-15.8$ days to $+49.1$ days after $B$-band
maximum. The decline rate of the light curve is $\Delta
m_{15}$($B$)$=1.39~\pm~0.05$ mag, which is intermediate between normal and
subluminous SNe Ia, and similar to that of the `transitional' Type Ia SN
2004eo.
  The spectral line profiles also closely resemble those of SN 2004eo. We were
able to observe SN 2012ht at very early phase, when it was still rising and was
about three magnitudes fainter than at the peak. The rise time to the $B$-band
maximum is estimated to be $17.6 \pm 0.5$ days and the time of the explosion is
MJD $56277.98 \pm 0.13$. SN 2012ht is the first transitional SN Ia whose rise
time is directly measured without using light curve templates, and the fifth SN
Ia overall. This rise time is consistent with those of the other four SNe
within the measurement error, even including the extremely early detection of
SN 2013dy. The rising part of the light curve can be fitted by a quadratic
function, and shows no sign of a shock-heating component due to the interaction
of the ejecta with a companion star. The rise time is significantly longer than
that inferred for subluminous SNe such as SN 1991bg, which suggests that a
progenitor and/or explosion mechanism of transitional SNe Ia are more similar
to normal SNe Ia rather than subluminous SNe Ia.
