Abstract: A communication device and a cryptographic key creation method are provided that enable efficient creation of cryptographic keys of which different error rates are required. A communication device (11) that performs communication with another communication device (12) through a transmission link includes a cryptographic key sharing section (1103) that share a first cryptographic key with the other communication device, an error rate control section (1115, 1105-1108) that creates second cryptographic keys with error rates according to purposes of use of the cryptographic keys from the first cryptographic key, and an accumulation section (111, 1112) that separately accumulates the plurality of second cryptographic keys with the different error rates.