Provided is a key migration device which can securely and reliably control the migration of keys. A migration authority (101) fetches a generation level which is the security level of a first electronic terminal (3011) and an output destination level which is the security level of a third electronic terminal (3013), decides whether the relationship between the generation level and the output destination level satisfies a predetermined condition when a request for fetching a collection of keys is received from the third electronic terminal (3013), outputs the key generated by the first electronic terminal (3011) among the collection of keys to the third electronic terminal (3013) if the predetermined condition is fulfilled, and restricts output to the third electronic terminal (3013) of the key generated by the first electronic terminal (3011) among the collection of keys if the predetermined condition is not fulfilled.