According to an embodiment, a communication device includes a plurality of communication processors, and one or more processors. Each of the communication processors is configured to generate an encryption key by quantum key distribution with an external communication device, encrypt data by using the generated encryption key, and transmit the data to the external communication device. The one or more processors are configured to: divide data requested to be transmitted by an application into a plurality of pieces of transmission data; and determine, from among the plurality of communication processors, one or more communication processors to be used for transmission of the divided plurality of pieces of the transmission data.