An information management method and system for managing consent for and use of information using a blockchain are provided. The information management method comprises: receiving a request to store a user agreement to the processing of the user's information from a service provider providing a service to the user; recording the user agreement on a blockchain; providing the service provider a response to the request to store the user agreement; receiving a third-party certification request for the provision of information from the user, regarding the information provided to the service provider; and providing a third-party certification for the provision of information to the user.