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The pattern of the ionospheric storm that was observed during the severe two-step geomagnetic storm on 19\textendash22 December 2015 in East Asia is investigated. The study is performed using a combination of vertical and oblique-incidence sounding, total electron content, riometer and magnetometer data obtained near 120\textdegree E meridian in 19\textendash66\textdegree N latitude zone. The revealed ionospheric disturbances are compared with the features of ionospheric storm, developed over the same region during the severe one step magnetic storm on 14\textendash16 December 2006. Compared magnetic storms are almost identical in the season and the onset time. They have approximately equal peak intensities (Dst = -155 nT and -162 nT), but differ noticeably in the duration of the main phases (19 h and 2.5 h) and the rate of the ring current field amplification. Through the comparison the ionospheric disturbances which are similar and dissimilar for both storms are revealed. Our study suggests that the main differences between ionospheric storms were observed during the initial and early recovery phases. They could be due to the differences between pre-storm states of the magnetosphere-ionosphere system as well as between interplanetary drivers.