  Star spot evolution is visible evidence of the emergence/decay of the
magnetic field on stellar surface, and it is therefore important for the
understanding of the underlying stellar dynamo and consequential stellar
flares. In this paper, we report the temporal evolution of individual star spot
area on the hot-Jupiter-hosting active solar-type star Kepler 17 whose transits
occur every 1.5 days. The spot longitude and area evolution are estimated (1)
from the stellar rotational modulations of Kepler data and (2) from the
brightness enhancements during the exoplanet transits caused by existence of
large star spots. As a result of the comparison, number of spots, spot
locations, and the temporal evolution derived from the rotational modulations
is largely different from those of in-transit spots. We confirm that although
only two light curve minima appear per rotation, there are clearly many spots
present on the star. We find that the observed differential intensity changes
are sometimes consistent with the spot pattern detected by transits, but they
sometimes do not match with each other. Although the temporal evolution derived
from the rotational modulation differs from those of in-transit spots to a
certain degree, the emergence/decay rates of in-transit spots are within an
order of magnitude of those derived for sunspots as well as our previous
research based only on rotational modulations. This supports a hypothesis that
the emergence/decay of sunspots and extremely-large star spots on solar-type
stars occur through the same underlying processes.
