  SN 2007bi is an extremely luminous Type Ic supernova. This supernova is
thought to be evolved from a very massive star, and two possibilities have been
proposed for the explosion mechanism. One possibility is a pair-instability
supernova with an M_{CO} ~ 100 M_sun CO core progenitor. Another possibility is
a core-collapse supernova with M_{CO} ~ 40 M_sun. We investigate the evolution
of very massive stars with main-sequence mass M_{MS} = 100 - 500 M_sun and Z_0
= 0.004, which is in the metallicity range of the host galaxy of SN 2007bi, to
constrain the progenitor of SN 2007bi. The supernova type relating to the
surface He abundance is also discussed. The main-sequence mass of the
progenitor exploding as a pair-instability supernova could be M_{MS} ~ 515 -
575 M_sun. The minimum main-sequence mass could be 310 M_sun when uncertainties
in the mass-loss rate are considered. A star with M_{MS} ~ 110 - 280 M_sun
evolves to a CO star, appropriate for the core-collapse supernova of SN 2007bi.
Arguments based on the probability of pair-instability and core-collapse
supernovae favour the hypothesis that SN 2007bi originated from a core-collapse
supernova event.
