  Sub-arcsecond ($0.^{\prime\prime}5$) images of H$_2$CO and CCH line emission
have been obtained in the $0.8$ mm band toward the low-mass protostar IRAS
15398-3359 in the Lupus 1 cloud as one of the Cycle 0 projects of the Atacama
Large Millimeter/Submillimeter Array. We have detected a compact component
concentrated in the vicinity of the protostar and a well-collimated outflow
cavity extending along the northeast-southwest axis. The inclination angle of
the outflow is found to be about $20^\circ$, or almost edge-on, based on the
kinematic structure of the outflow cavity. This is in contrast to previous
suggestions of a more pole-on geometry. The centrally concentrated component is
interpreted by use of a model of the infalling rotating envelope with the
estimated inclination angle, and the mass of the protostar is estimated to be
less than $0.09\ M_\odot$. Higher spatial resolution data are needed to infer
the presence of a rotationally supported disk for this source, hinted at by a
weak high-velocity H$_2$CO emission associated with the protostar.
