We investigate the ⑀Ј/⑀ for K→ in a sequential fourth generation model. By giving the basic formulas for ⑀Ј/⑀ in this model, we analyze the numerical results which are dependent on m t Ј and the imaginary part of the fourth CKM factor, ImV t Ј s * V t Ј d ͑or V t Ј s * V t Ј d and the fourth generation CKM matrix phase ). We find that, unlike the SM, when taking the central values of all parameters for ⑀Ј/⑀, the values of ⑀Ј/⑀ can easily fit to the current experimental data for all values of hadronic matrix elements estimated from various approaches. Also, we show that the experimental values of ⑀Ј/⑀ and rare K decays can provide a strong constraint on both mass and mixing of the fourth generation quark. When taking the values of hadronic matrix elements from the lattice or 1/N expansion calculations, a large region of the up-type quark mass m t Ј is excluded.