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We have analyzed the OCS, H$_2$CS, CH$_3$OH, and HCOOCH$_3$ data observedtoward the low-mass protostar IRAS 16293--2422 Source B at a sub-arcsecondresolution with ALMA. A clear chemical differentiation is seen in theirdistributions; OCS and H$_2$CS are extended with a slight rotation signature,while CH$_3$OH and HCOOCH$_3$ are concentrated near the protostar. Such achemical change in the vicinity of the protostar is similar to the companion(Source A) case. The extended component is interpreted by theinfalling-rotating envelope model with a nearly face-on configuration. Theradius of the centrifugal barrier of the infalling-rotating envelope is roughlyevaluated to be ($30-50$) au. The observed lines show the inverse P-Cygniprofile, indicating the infall motion with in a few 10 au from the protostar.The nearly pole-on geometry of the outflow lobes is inferred from the SiOdistribution, and thus, the infalling and outflowing motions should coexistalong the line-of-sight to the protostar. This implies that the infalling gasis localized near the protostar and the current launching points of the outflowhave an offset from the protostar. A possible mechanism for this configurationis discussed.

Chemical and Physical Picture of IRAS 16293-2422 Source B at a Sub-arcsecond Scale Studied with ALMA