A frame-merging method is adapted for a network that includes mesh and terminal units, in which any two units capable of communication form a communication pair, and one of the units operates as a key unit to transmit pending frames according to the frame-merging method. The frame-merging method includes: determining whether the key unit is a mesh or a terminal unit; for the communication pair recorded in each pending frame, selecting a suitable scheme from a plurality of frame-merging schemes, and extracting at least one of the pending frames from among the pending frames for use as part or all of a priority frame set; and comparing a total size of all frames included in the priority frame set with a suitable frame size, so as to determine whether the key unit is to send an aggregated frame. A frame-merging apparatus is also disclosed.