Abstract: A hybrid cloud-based security service apparatus for securing confidential data includes a cloud service module assigning an analysis identifier to data input by a user of a network connected to a cloud and receiving a request for delivery of encrypted data from the user, a key generation service unit located in an on-premise connected to the cloud and generating an encryption key based on the analysis ID, an encryption processing unit encrypting the data using the encryption key and a predetermined encryption algorithm, a logical operation unit performing a logical operation on the encryption key used to encrypt the data to invert predetermined bits of the encryption key, and a decryption service module receiving the encrypted data and the encryption key from the on-premise, restoring the encryption key by performing a logical operation, and decrypting the encrypted data using the restored encryption key and a decryption algorithm.