Provided are a secure device and method for preventing a side channel attack. The secure device includes a secure module converting plaintext data received from the outside into ciphertext data to thereby store the converted ciphertext data, or converting stored ciphertext data into plaintext data to thereby output the converted plaintext data, and a side channel attack sensing module sensing a side channel attack upon the secure module, and, according to the sensing result, allowing the secure module to stop operating, inducing malfunctions of the secure module, delaying operations of the secure module, or making the secure module a device having the secure module disabled. The secure device can safely protect an internal security algorithm and data from the side channel attack.