A nonvolatile memory device and a method of programming the device includes storing first data in first main and sub-registers and storing second data in second main and sub-registers, performing first program and verification operations on first memory cells based on the first data stored in the first main register, storing a result of the first verification operation in the first main register, performing a second program operation on second memory cells based on the second data stored in the second main register, changing the result of the first verification operation, stored in the first main register, into the first data stored in the first sub-register, performing an additional verification operation on the first memory cells on which the first verification operation has been completed, storing a result of the additional verification operation in the first main register, and performing a second verification operation on the second memory cells.