A three-dimensional multi-frequency antenna includes a substrate; a shorting wall vertically formed on a first edge of the substrate; a radiation element including a first radiator corresponding to a first resonance frequency band, and a second radiator corresponding to a second resonance frequency band, the first radiator and the second radiator capable of generating a frequency-multiplying third resonance frequency extending toward opposite directions; and a connection element, for connecting the shorting wall and the radiation element, separated from a second edge of the substrate by a gap; wherein the width of the radiation element and the gap conforms to a specific ratio.