A terminal set of an electrical connector includes signal terminal duos and ground terminal duos. The signal terminal duos have two signal terminals. The signal terminals are spaced apart by a first distance and each have a first recess. The direction of the depth of the first recess equals the longitudinal direction of the signal terminals. The ground terminal duos have two ground terminals. The signal terminal duos are disposed between the ground terminals. The ground terminals each have a second recess. The direction of the depth of the second recess equals the longitudinal direction of the ground terminals. The ground terminal and the adjacent signal terminal are spaced apart by a second distance. The first distance is shorter than the second distance. The ground terminals each partially bulges out transversely to form at least a bulging portion. The terminal set features terminal electrical impedance and alleviated inter-terminal resonance.