A compact ultrawideband (UWB) antenna with a band-notch function is proposed for laptop applications. The band-notch function is realized by a half-wavelength parasitic element printed on the rear side of the substrate. The impedance bandwidth (VSWR < 2) of the antenna is 3.1 ~ 11.4 GHz (114%) with a notched frequency from 5.05 to 5.90 GHz. The antenna has a fairly good omnidirectional pattern, and the average gain is -3.0 ~ -1.2 dBi over the UWB frequency band except for the notched frequency band. The performance of the proposed antenna is confirmed by simulation and measurement results.