  We have carried out near-infrared JHK spectroscopy of a gravitationally
lensed submillimeter galaxy SMM J14011+0252 at z=2.565, using OHS and CISCO on
the Subaru telescope. This object consists of two optical components, J1 and
J2, which are lensed by the cluster Abell 1835. J1 suffers additional strong
lensing by a foreground galaxy at z=0.25 in the cluster. The rest-optical
H-alpha, H-beta, and [O II]3727 lines are detected in both J1 and J2, and [N
II]6548,6583 lines are also detected in J1. A diagnosis of emission-line ratios
shows that the excitation source of J1 is stellar origin, consistent with
previous X-ray observations. The continua of J1 and J2 show breaks at rest
4000A, indicating relatively young age. Combined with optical photometry, we
have carried out model spectrum fitting of J2 and find that it is a very young
(~50 Myr) galaxy of rather small mass (~10e8 M_sol) which suffers some amount
of dust extinction. A new gravitational lensing model is constructed to assess
both magnification factor and contamination from the lensing galaxy of the
component J1, using HST-F702W image. We have found that J1 suffers strong
lensing with magnification of ~30, and its stellar mass is estimated to be <
10e9 M_sol. These results suggest that SMM J14011+0252 is a major merger system
at high redshift that undergoes intense star formation, but not a formation
site of a giant elliptical. Still having plenty of gas, it will transform most
of the gas into stars and will evolve into a galaxy of < 10e10 M_sol.
Therefore, this system is possibly an ancestor of a less massive galaxy such as
a mid-sized elliptical or a spiral at the present.
