The present invention discloses to an SMA connector, a preferable embodiment of which comprises a body acting as ground, a central conductor existing in the inner part of the ground, an insulator with a predetermined dielectric constant existing between the body and the central conductor, a first step transition part formed in the body, a taper formed in the central conductor in order to improve RF characteristics and to fix the central conductor and the insulator, and a second step transition part formed in the central conductor corresponding to the first step transition part to improve RF characteristics.