  Using the HST WFPC2/NICMOS archival data of the Hubble Deep Field North, we
construct the nearly complete sample of the Mv <-20 (~L*+1) galaxies to z=2,
and investigate when the Hubble sequence appeared, namely, the evolution of the
morphology, colors, and the comoving number density of the sample. Even if
taking into account of the uncertainty of the photometric redshift technique,
the number density of relatively bright bulge-dominated galaxies in the HDF-N
decrease significantly at z>1, and their rest-frame U-V color distribution is
wide-spread over 0.5<z<2. On the other hand, while the number density of both
disk-dominated and irregular galaxies does not show significant change at z<2,
their distribution of the rest-frame U-V color alters at z~1.5: there is no
relatively red (rest U-V>0.3) galaxies at z>1.5, while the significant fraction
of these red disk-dominated or irregular galaxies exists at z<1.5. These
results suggest that the significant evolution of the Hubble sequence which is
seen in the present Universe occurs at 1<z<2.
