Provided is a method for constructing a key graph for multi-group multi-casting service and managing a key. The method includes: searching for a user group set (common group set) having the same access right to each resource combination comprising multiple resource selected from resources for a service and non-overlapping with other resource combinations by using an access right relations between user groups and the resource; and constructing a key graph by interconnecting a user group key and a resource key using the access right relation, where user groups pertaining to the searched common group set are connected to corresponding resources via intermediate nodes.