This paper presents an ultra- wideband (UWB) resonator and a bandpass filter (BPF) consisting of quasi- lumped elements using a microstrip line (MSL). First of all, a resonator using a high-impedance inductive line and a gap capacitor is examined by an electromagnetic simulator. The simulated results of the resonator show UWB bandpass characteristics with two controllable stop- bands by adjusting the element values and the length of the resonator. Secondly, an UWB-BPF using the presented resonator is proposed, fabricated, simulated and measured. It is confirmed that desired UWB bandpass characteristics are realized by controlling two stopband characteristics.