  We present the results from our narrow-band imaging surveys of HAEs at z=2.2
and z=2.5 in the Subaru/XMM-Newton Deep survey Field with near-infrared camera
MOIRCS on Subaru Telescope. We have constructed a clean sample of 63
star-forming galaxies at z=2.2 and 46 at z=2.5. For 12 (or ~92%) out of 13
H\alpha emitters (HAEs) at z=2.2, their H\alpha emission lines have been
successfully detected by the spectroscopy. While about 42% of the red, massive
HAEs with M_*>10^{10.8} M_\odot contain AGNs, most of the blue, less massive
ones are likely to be star-forming galaxies. This suggests that the AGN may
play an important role in galaxy evolution at the late stage of truncation. For
the HAEs excluding possible AGNs, we estimate the gas-phase metallicities on
the basis of [N~{\sc ii}]/H\alpha ratios, and find that the metallicities of
the H\alpha selected galaxies at z=2.2 are lower than those of local
star-forming galaxies at fixed stellar mass, as shown by previous studies.
Moreover, we present and discuss the so-called "main sequence" of star-forming
galaxies at z>2 based on our unique sample of HAEs. By correlating the level of
dust extinction with the location on the main sequence, we find that there are
two kinds/modes of dusty star-forming galaxies: star-bursting galaxies and
metal-rich normal star-forming galaxies.
