In this paper, a novel resonator using ring type DGS is proposed for improvement of phase noise characteristics that is weak point of oscillator using planar type microstrip line resonator, and oscillator for 5.8 GHz band is designed using proposed DGS resonator. The ring type DGS resonator is composed of DGS cell etched on ground plane under $50{Omega}$ microstrip line. At the fundamental frequency of 5.8 GHz, 7.6 dBm output power and -82.7 dBc@100kHz phase noise have been measured for oscillator with ring type DGS resonator. We designed the voltage controlled oscillator using proposed the DGS resonator with varactor diodes placed between gaps of DGS. Thus, due to its simple fabrication process and planar type, it is expected that the technique in this paper can be widely used for low phase noise oscillators for both MIC and MMIC applications.