The invention provides an ion implantation device and an adjustment method of beam current density distribution. The irradiation areas of band-shaped ion beams in an amount of m (m is an integer over 2) at least partially overlap. In an ion implantation device which achieves regulated implantation amount distribution on a glass substrate, the beam current density distribution of each band-shaped ion beam can be adjusted with high efficiency. Each band-shaped ion beam is set as a target distribution of an adjustment target as a beam current density distribution. According to a pre-determined sequence, the beam current density distribution from a first band-shaped ion beam to a (m-1)th band-shaped ion beam, enabling the band-shaped ion beam to enter into a first allowing range with respect to the target distribution. Based on the difference between the distribution obtained from the adjustment result of each band-shaped ion beam and the distribution obtained from the target distribution of ion beams in an amount of m, new target distribution for adjusting a mth beam current density distribution is set, and the mth beam current density distribution is adjusted, enabling the mth beam current density distribution to enter into a second allowing range with respect to the new target distribution.