A mobile device with high radiation efficiency includes a ground element, a first radiation element, a second radiation element, a third radiation element, a fourth radiation element, a dielectric substrate, a speaker body, and a cable. The first radiation element and the fourth radiation element are coupled to the ground element. The second radiation element and the third radiation element are coupled to a feeding point. An antenna structure is formed by the first radiation element, the second radiation element, the third radiation element, and the fourth radiation element. The speaker body has a first vertical projection on the dielectric substrate, and the first vertical projection at least partially overlaps the third radiation element. The cable is coupled to the speaker body. The cable has a second vertical projection on the dielectric substrate, and the second vertical projection does not overlap the antenna structure at all.