[en] After the discovery of high T_c cuprates, there has been much progress in understanding of the field vs. temperature phase diagram of type II superconductors, and many novel superconducting phenomena in nonzero magnetic fields have been detected primarily in novel materials with strong electron correlation. In particular, a remarkable Pauli paramagnetic depairing with their origin in the strong correlation tends to strongly affect the vortex lattice structure. The present status of theories on superconducting vortex states will be reviewed here. (author)