Provided is an encryption device which can effectively use a hardware encryption engine and reduce a packet processing delay of a real time application. In this device, an approval unit (230) judges whether it is possible to use an HW cipher unit (264) corresponding to a secure application requested for encryption operation, i.e., whether an encryption resource is not used. A priority processing approval unit (240) calculates a priority of a cryptographic operation in the secure application of the request source. If the HW cipher unit (264) cannot be used, the priority of a secure application currently allocated to the HW cipher unit (264) is compared to that of the secure application requesting for the cryptographic operation. If the secure application of the request source has a higher priority, the currently allocated secure application is released from the HW cipher unit and the secure application of the request source is allocated to the HW cipher unit (264). The secure application which has been released is allocated to an SW cipher unit (266).