Provided is a transmission power allocation method based on reinforcement learning with an efficient user clustering method. According to an embodiment of the present disclosure, a transmission power allocation method based on user clustering and reinforcement learning of a base station in a non-orthogonal multiple access (NOMA) system includes a sorting step of sorting channel gains of user equipments located in a coverage of the base station in a size order, a clustering step of allocating the user equipment to each cluster based on the size order, and a power allocation step of allocating power to each user equipment included in the cluster by using a quality function based on a state and an action.