  We carried out spectroscopic observations with Subaru/HDS of 50 solar-type
superflare stars found from Kepler data. More than half (34 stars) of the
target stars show no evidence of the binary system, and we confirmed
atmospheric parameters of these stars are roughly in the range of solar-type
stars. We then conducted the detailed analyses for these 34 stars. First, the
value of the "$v\sin i$" (projected rotational velocity) measured from
spectroscopic results is consistent with the rotational velocity estimated from
the brightness variation. Second, there is a correlation between the amplitude
of the brightness variation and the intensity of Ca II IR triplet line. All the
targets expected to have large starspots because of their large amplitude of
the brightness variation show high chromospheric activities compared with the
Sun. These results support that the brightness variation of superflare stars is
explained by the rotation of a star with large starspots.
