Two sesquiterpene lactones were isolated from methanol extracts of the whole plants of Youngia japonica (L.) DC. by the silica gel column chromatography and recrystallization. On the basis of spectrometric studies including $^1H-NMR,;^{13}C-NMR,;DEPT,;^1H-^1H;COSY,;^{13}C-^1H;COSY$, IR and MS, compounds 1 and 2 were identified as derivatives of 10(14)-guaien-12, 6-olide, isoamberboin and isolipidiol, respectively. This is the first report on the isolation of isoamberboin and isolipidiol from Youngia japonica (L.) DC.