A signal transmission connector includes an insulating body, a plurality of first terminals, a plurality of second terminals, and a rear casing. The insulating body has a dielectric constant of about 3 to 3.4. The first and second terminals are disposed on the insulating body. The first and second terminals have widths of about 0.36 to 0.42 mm. The rear casing is assembled at the second end of the insulating body. The rear casing envelops the first and the second terminals. The rear casing has a dielectric constant of about 3.5 to 3.8. The connector provides adjustable impedance without modifications to the terminal structures and also reduces cost.