Program method of blocking program error for multi bit flash memory device

A program method of blocking program error for a multi bit flash memory device is provided to solve an error generated by memory cells which is programmed in a high speed. According to a program method of a multi bit flash memory device, memory cells having a target threshold voltage among selected memory cells are detected and then the detected memory cells are set as program prohibit, before programming. Programming is performed to program the selected memory cells to have the target threshold voltage. While the programming is performed, memory cells except the memory cells set as program prohibit among the selected memory cells are programmed with the target threshold voltage.