[Problem] Provided are a management device and a cryptocurrency system capable of smoothly operating an entire system by detecting fraud on cryptocurrencies without using enormous calculation amounts.
[Solution] A management device connected to a plurality of user devices via a network, the management device including: an issued information storage area that stores a cryptocurrency ID of an issued cryptocurrency; an account information storage area that stores account information in association with one or a plurality of cryptocurrency IDs; and a history information storage area that stores history information of a cryptocurrency in association with a cryptocurrency ID.