Provided is a game control method carried out by a game control device connected to communication terminals used by users who play a game. The device has a storage unit for storing group information indicative of a group consisting of users and game piece information indicative of game pieces constituting one item. The method includes giving a game piece to each user in accordance with a user operation to his/her communication terminal; storing obtained game piece information indicative of the game piece given to each user in the storage unit; determining whether all of the game pieces necessary to constitute the one item indicated by the game piece information are given to users constituting a group indicated by the group information based on the obtained game piece information; and giving a reward to users constituting the group if it is determined that all of the game pieces are given.