In this paper. Rijndael cipher algorithm is implemented by a hardware. It was selected as the AES(Advanced Encryption Standard) by NIST. It has structure that round operation divided into 2 subrounds and subrounds are pipelined to calculate efficiently. It takes 5 clocks for one-round. The AES-128 cipher algorithm is implemented for hardware by ALTERA FPGA, and, analyzed the performance. The AES-128 cipher algorithm has approximately 424 Mbps encryption rate for 166Mhz max clock frequency. In case of decryption, it has 363 Mbps decryption rate fu 142Mhz max clock frequency. In case of cipher core, it has 320Mbps encryptionㆍdecryption rate for 125Mhz max clock frequency.