The Belle II detector is a general-purpose spectrometer which is being built at the asymmetric
electron-positron collider SuperKEKB in Japan. The experiment aims at more precise measure-
ment of the Standard Model contribution and overconstraining of the unitarity triangle in the B
and D meson decays. The 2-layer active pixel detector based on the novel DEPFET technology is
the innermost detector in the experiment and a part of the vertex detector which consists of pixel
detector and double-sided silicon strip detector. The pixel detector provides excellent spacial res-
olution of around 10 μm and low material budget resulting in 0.21% X$_0$ /layer. The detector is used
to measure the precise position of the primary decay vertex. The energy loss in the detector may
also be used for the identification of the incident particles. The working principle of the detector
as well as the current development status are presented in the paper.