A ring millimeter-wave filter is a three-dimensional dual-mode ring filter. The ring millimeter-wave filter makes use of a three-dimensional coupling architecture as the feed of a filter to conquer the limit of the smallest spacing of a planar circuit made by the low-temperature cofired ceramic (LTCC) process so as to achieve the required coupling. Moreover, through the design of an embedded microstrip line, more than 20% of the filter area can be saved to facilitate integration with other components.