The present invention relates to a programmable-gate-array copy protection method and a system which prevent unauthorized copying of an FPGA program. A copy protection method for a field-programmable gate array, the method comprising a step of causing a user-specific gate array to boot a user circuit data to the field-programmable gate array, the user-specific gate array being connected to the field-programmable gate array and a memory device in which the user circuit data is stored and being pre-programmed at a semiconductor-vender's factory.