Frames of different priority levels are queued in a plurality of queues, e.g., first priority queue, second priority queue and third priority queue. If it is judged that a lower priority frame can be completely transmitted by the timing of transmitting a higher-priority frame based on the frame length, the lower-priority frame is transmitted, and otherwise, the lower-priority frame is not transmitted. Accordingly, frame transmission control that is applicable to fixed-length frames and variable-length frames is realized in a frame scheduler for an apparatus having a function of outputting frames. Also, priority-based control of frames which is suitable for a layer 2 switch or the like and which is adaptable to processing in a high-speed network is realized without providing an IP fragment.