  We study the resonance spectroscopy of 7He in the 4He+n+n+n cluster model,
where the motion of valence neutrons is described in the cluster orbital shell
model. Many-body resonances are treated on the correct boundary condition as
the Gamow states in the complex scaling method. We obtain five resonances and
investigate their properties from the configurations. In particular, the 1/2-
state is found in a low excitation energy of 1.1 MeV with a width of 2.2 MeV,
while the experimental determination of the position of this state is not so
clear. We also evaluate the spectroscopic factors of the 6He-n components in
the obtained 7He resonances. The importance of the 6He(2+) state is shown in
several states of 7He.
